* Atmel GPIO controller (PIO)

Required properties:
- compatible: "atmel,<chip>-gpio", where <chip> is at91rm9200 or at91sam9x5.
- reg: Should contain GPIO controller registers location and length
- interrupts: Should be the port interrupt shared by all the pins.
- #gpio-cells: Should be two.  The first cell is the pin number and
  the second cell is used to specify optional parameters to declare if the GPIO
  is active high or low. See gpio.txt.
- gpio-controller: Marks the device node as a GPIO controller.
- interrupt-controller: Marks the device node as an interrupt controller.
- #interrupt-cells: Should be two. The first cell is the pin number and the
  second cell is used to specify irq type flags, see the two cell description
  in interrupt-controller/interrupts.txt for details.

optional properties:
- #gpio-lines: Number of gpio if absent 32.


Example:
	pioA: gpio@fffff200 {
		compatible = "atmel,at91rm9200-gpio";
		reg = <0xfffff200 0x100>;
		interrupts = <2 4>;
		#gpio-cells = <2>;
		gpio-controller;
		#gpio-lines = <19>;
		interrupt-controller;
		#interrupt-cells = <2>;
	};