Device-Tree bindings for drm hdmi driver

Required properties:
- compatible: value should be one among the following:
	1) "samsung,exynos5-hdmi" <DEPRECATED>
	2) "samsung,exynos4210-hdmi"
	3) "samsung,exynos4212-hdmi"
- reg: physical base address of the hdmi and length of memory mapped
	region.
- interrupts: interrupt number to the cpu.
- hpd-gpio: following information about the hotplug gpio pin.
	a) phandle of the gpio controller node.
	b) pin number within the gpio controller.
	c) optional flags and pull up/down.

Example:

	hdmi {
		compatible = "samsung,exynos4212-hdmi";
		reg = <0x14530000 0x100000>;
		interrupts = <0 95 0>;
		hpd-gpio = <&gpx3 7 1>;
	};
