MOXA ART GPIO Controller

Required properties:

- #gpio-cells : Should be 2, The first cell is the pin number,
		the second cell is used to specify polarity:
			0 = active high
			1 = active low
- compatible : Must be "moxa,moxart-gpio"
- reg : Should contain registers location and length

Example:

	gpio: gpio@98700000 {
		gpio-controller;
		#gpio-cells = <2>;
		compatible = "moxa,moxart-gpio";
		reg =	<0x98700000 0xC>;
	};