* Marvell EBU GPIO controller

Required properties:

- compatible : Should be "marvell,orion-gpio", "marvell,mv78200-gpio"
  or "marvell,armadaxp-gpio". "marvell,orion-gpio" should be used for
  Orion, Kirkwood, Dove, Discovery (except MV78200) and Armada
  370. "marvell,mv78200-gpio" should be used for the Discovery
  MV78200. "marvel,armadaxp-gpio" should be used for all Armada XP
  SoCs (MV78230, MV78260, MV78460).

- reg: Address and length of the register set for the device. Only one
  entry is expected, except for the "marvell,armadaxp-gpio" variant
  for which two entries are expected: one for the general registers,
  one for the per-cpu registers.

- interrupts: The list of interrupts that are used for all the pins
  managed by this GPIO bank. There can be more than one interrupt
  (example: 1 interrupt per 8 pins on Armada XP, which means 4
  interrupts per bank of 32 GPIOs).

- interrupt-controller: identifies the node as an interrupt controller

- #interrupt-cells: specifies the number of cells needed to encode an
  interrupt source. Should be two.
  The first cell is the GPIO number.
  The second cell is used to specify flags:
    bits[3:0] trigger type and level flags:
      1 = low-to-high edge triggered.
      2 = high-to-low edge triggered.
      4 = active high level-sensitive.
      8 = active low level-sensitive.

- gpio-controller: marks the device node as a gpio controller

- ngpios: number of GPIOs this controller has

- #gpio-cells: Should be two. The first cell is the pin number. The
  second cell is reserved for flags, unused at the moment.

Example:

		gpio0: gpio@d0018100 {
			compatible = "marvell,armadaxp-gpio";
			reg = <0xd0018100 0x40>,
			    <0xd0018800 0x30>;
			ngpios = <32>;
			gpio-controller;
			#gpio-cells = <2>;
			interrupt-controller;
			#interrupt-cells = <2>;
			interrupts = <16>, <17>, <18>, <19>;
		};
