1. Field of the Invention The present invention relates to an integrated circuit and, more particularly, to an integrated circuit having a plurality of chips formed on one semiconductor substrate. 2. Description of the Prior Art In a conventional integrated circuit, a power supply voltage and a ground potential of one chip are supplied to another chip through wire bonding. Alternatively, for a plurality of chips formed on one semiconductor substrate, the respective power supply voltages and ground potentials are shared among the chips through the one semiconductor substrate. The power supply voltages and ground potentials supplied from one chip to another are usually about several volts. Therefore, high-speed signal transmission requires large wiring lengths and is subject to the influence of external noise. As a result, the high-speed signal transmission becomes difficult. In a typical conventional integrated circuit, the power supply voltages and ground potentials are supplied from a certain chip to another chip through wire bonding. In this case, wiring resistance can be decreased. In addition, when the power supply voltages and ground potentials are supplied from the one chip to another through bonding wires, the bonding wires serve as a good low-pass filter. For the same reason, noise of several tens of megahertz or higher components is removed. When the power supply voltages and ground potentials are supplied from the one chip to another chip through the one semiconductor substrate, noise due to such a high-frequency component cannot be removed. In other words, when the power supply voltages and ground potentials are supplied from the one chip to another chip through wire bonding or through the one semiconductor substrate, signal transmission characteristics may not meet required standards for high-speed signal transmission. Therefore, there is a demand for an integrated circuit that satisfies the above requirements and can transmit signals at high speeds. An object of the present invention is to provide an integrated circuit that allows high-speed signal transmission. Another object of the present invention is to provide an integrated circuit that allows signal transmission at high speeds without increasing the number of bonding wires. According to a first aspect of the present invention, an integrated circuit having a plurality of chips formed on one semiconductor substrate includes a control chip for performing transmission/reception of signals between two different chips, and a power supply electrode for supplying the power supply voltage to the control chip. The control chip includes an internal power supply terminal for receiving the power supply voltage supplied from a first chip through the power supply electrode and transmitting the received power supply voltage to the power supply electrode, and a ground terminal connected to a ground of the first chip. According to a second aspect of the present invention, an integrated circuit having a plurality of chips formed on one semiconductor substrate includes a control chip for performing transmission/reception of signals between two different chips, a first chip that supplies the power supply voltage to the control chip through a power supply electrode, and a second chip that supplies the power supply voltage to the control chip through a power supply electrode. The control chip includes an internal power supply terminal for receiving the power supply voltage supplied from the first chip through the power supply electrode and transmitting the received power supply voltage to the power supply electrode, and a ground terminal connected to a ground of the second chip. In accordance with the present invention, when a plurality of chips are formed on one semiconductor substrate, the control chip for performing transmission/reception of signals between the chips and the substrate is provided with a function of an internal voltage supply source for generating a power supply voltage for each chip from a voltage supplied through the one semiconductor substrate. Therefore, a plurality of chips formed on one semiconductor substrate share the power supply voltage. This reduces the number of bonding wires that are required for supplying the power supply voltage to a chip from an external device and that must be cut off in accordance with the chip size. As a result, a high-speed signal transmission circuit can be realized. Additional advantages and functions of the invention will become apparent from the following detailed description of the preferred embodiments, which illustrate various embodiments of the invention. The detailed description is not to be taken in a limiting sense, but to provide a full understanding of the invention. According to a third aspect of the present invention, an integrated circuit having a plurality of chips formed on one semiconductor substrate includes a plurality of chips formed on one semiconductor substrate. Each chip includes a control electrode for performing transmission/reception of signals between a plurality of chips, and a power supply electrode connected to the control electrode and for supplying a power supply voltage from a chip other than the corresponding chip to the control electrode. According to a fourth aspect of the present invention, an integrated circuit having a plurality of chips formed on one semiconductor substrate includes a control chip for performing transmission/reception of signals between two different chips, a first chip that supplies the power supply voltage to the control chip through a power supply electrode, and a second chip that supplies the power supply voltage to the control chip through a power supply electrode. The control chip includes an internal power supply terminal for receiving the