Nintendo Wii (Hollywood) GPIO controller

Required properties:
- compatible: "nintendo,hollywood-gpio"
- reg: Physical base address and length of the controller's registers.
- gpio-controller: Marks the device node as a GPIO controller.
- #gpio-cells: Should be <2>. The first cell is the pin number and the
  second cell is used to specify optional parameters:
   - bit 0 specifies polarity (0 for normal, 1 for inverted).

Optional properties:
- ngpios: see Documentation/devicetree/bindings/gpio/gpio.txt
- interrupt-controller: Marks the device node as an interrupt controller.
- #interrupt-cells: Should be two.
- interrupts: Interrupt specifier for the controller's Broadway (PowerPC)
  interrupt.
- interrupt-parent: phandle of the parent interrupt controller.

Example:

	GPIO: gpio@d8000c0 {
		#gpio-cells = <2>;
		compatible = "nintendo,hollywood-gpio";
		reg = <0x0d8000c0 0x40>;
		gpio-controller;
		ngpios = <24>;
	}