[media] media: rc: meson: document device tree bindings

* Amlogic Meson IR remote control receiver

Required properties:

 - compatible	: should be "amlogic,meson6-ir"

 - reg		: physical base address and length of the device registers

 - interrupts	: a single specifier for the interrupt from the device

Example:

	ir-receiver@c8100480 {

		compatible= "amlogic,meson6-ir";

		reg = <0xc8100480 0x20>;

		interrupts = <0 15 1>;

	};