Bindings for sony video selector

Required properties:
- compatible : "sony,video_selector"
- mux-controls : mux controller node to use for operating the mux
  Refer Documentation/devicetree/bindings/mux/mux-controller.txt
- video_sel-supply : phandle to the regulator for pcont_1 supply

Example:

	&i2c2 {
		mux: mux-controller {
			compatible = "njr,njw1327";
			reg = <0x4b>;
			#mux-control-cells = <0>;
		};
	};

	video_sel: video_selector {
		compatible = "sony,video_selector";
		mux-controls = <&mux>;
		video_sel-supply = <&pcont_1>;
	};
