media: dt-bindings: media: Add Amlogic Meson AO-CEC bindings

* Amlogic Meson AO-CEC driver

The Amlogic Meson AO-CEC module is present is Amlogic SoCs and its purpose is

to handle communication between HDMI connected devices over the CEC bus.

Required properties:

  - compatible : value should be following

	"amlogic,meson-gx-ao-cec"

  - reg : Physical base address of the IP registers and length of memory

	  mapped region.

  - interrupts : AO-CEC interrupt number to the CPU.

  - clocks : from common clock binding: handle to AO-CEC clock.

  - clock-names : from common clock binding: must contain "core",

		  corresponding to entry in the clocks property.

  - hdmi-phandle: phandle to the HDMI controller

Example:

cec_AO: cec@100 {

	compatible = "amlogic,meson-gx-ao-cec";

	reg = <0x0 0x00100 0x0 0x14>;

	interrupts = <GIC_SPI 199 IRQ_TYPE_EDGE_RISING>;

	clocks = <&clkc_AO CLKID_AO_CEC_32K>;

	clock-names = "core";

	hdmi-phandle = <&hdmi_tx>;

};