Ingenic jz47xx GPIO controller

That the Ingenic GPIO driver node must be a sub-node of the Ingenic pinctrl
driver node.

Required properties:
--------------------

 - compatible: Must contain one of:
    - "ingenic,jz4740-gpio"
    - "ingenic,jz4770-gpio"
    - "ingenic,jz4780-gpio"
 - reg: The GPIO bank number.
 - interrupt-controller: Marks the device node as an interrupt controller.
 - interrupts: Interrupt specifier for the controllers interrupt.
 - #interrupt-cells: Should be 2. Refer to
   ../interrupt-controller/interrupts.txt for more details.
 - gpio-controller: Marks the device node as a GPIO controller.
 - #gpio-cells: Should be 2. The first cell is the GPIO number and the second
    cell specifies GPIO flags, as defined in <dt-bindings/gpio/gpio.h>. Only the
    GPIO_ACTIVE_HIGH and GPIO_ACTIVE_LOW flags are supported.
 - gpio-ranges: Range of pins managed by the GPIO controller. Refer to
   'gpio.txt' in this directory for more details.

Example:
--------

&pinctrl {
	#address-cells = <1>;
	#size-cells = <0>;

	gpa: gpio@0 {
		compatible = "ingenic,jz4740-gpio";
		reg = <0>;

		gpio-controller;
		gpio-ranges = <&pinctrl 0 0 32>;
		#gpio-cells = <2>;

		interrupt-controller;
		#interrupt-cells = <2>;

		interrupt-parent = <&intc>;
		interrupts = <28>;
	};
};