ARM PL061 GPIO controller

Required properties:
- compatible : "arm,pl061", "arm,primecell"
- #gpio-cells : Should be two. 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)
- gpio-controller : Marks the device node as a GPIO controller.
- interrupts : Interrupt mapping for GPIO IRQ.
- baseidx : base index for the GPIO numeration.

Example of gpio-controller nodes:
	gpio0 {
		#gpio-cells = <2>;
		compatible = "arm,pl061", "arm,primecell";
		gpio-controller;
		reg = <0x0 0xfd887000 0x0 0x1000>;
		interrupts = <0 2 4>;
		clocks = <&sbclk>;
		clock-names = "apb_pclk";
		baseidx = <0>;
	};

	gpio1 {
		#gpio-cells = <2>;
		compatible = "arm,pl061", "arm,primecell";
		gpio-controller;
		reg = <0x0 0xfd888000 0x0 0x1000>;
		interrupts = <0 3 4>;
		clocks = <&sbclk>;
		clock-names = "apb_pclk";
		baseidx = <8>;
	};

