Device-Tree bindings for Xilinx Video On Screen Display(OSD)

Xilinx OSD provides the multiplane support. Some properties can be configured
in IP synthesis.

Required properties:
 - compatible: value should be "xlnx,v-osd-5.01.a"
 - reg: base address and size of the OSD IP
 - xlnx,num-layers: the number of layers(up to 8) supported by OSD
 - xlnx,screen-width: the maximum size(up to 4096) of screen pixel width by OSD

Example:

	v_osd_0: v-osd@40040000 {
		compatible = "xlnx,v-osd-5.01.a";
		reg = <0x40040000 0x10000>;
		xlnx,num-layers = <2>;
		xlnx,screen-width = <1920>;
	};
