* Hannstar CABC device tree bindings

The Hannstar CABC function may turn a display plane's backlight
automatically according to the content shown on the plane.  The
function is controlled(enabled/disabled) by a GPIO.

Required properties:
- compatible : Should be "hannstar,cabc".

Each standalone CABC gpio is represented as a sub-node of "hannstar_cabc":
Required subnode properties:
- gpios: OF device-tree gpio specification.

Optional subnode properties:
- cabc-enable: Provide this bool property if you want to enable the CABC feature.

Example:
	hannstar_cabc {
		compatible = "hannstar,cabc";

		lvds0 {
			gpios = <&gpio6 15 GPIO_ACTIVE_HIGH>;
		};

		lvds1 {
			gpios = <&gpio6 16 GPIO_ACTIVE_HIGH>;
		};
	};