[media] dt-bindings: Add a binding for Mediatek Video Processor

* Mediatek Video Processor Unit

Video Processor Unit is a HW video controller. It controls HW Codec including

H.264/VP8/VP9 Decode, H.264/VP8 Encode and Image Processor (scale/rotate/color convert).

Required properties:

  - compatible: "mediatek,mt8173-vpu"

  - reg: Must contain an entry for each entry in reg-names.

  - reg-names: Must include the following entries:

    "tcm": tcm base

    "cfg_reg": Main configuration registers base

  - interrupts: interrupt number to the cpu.

  - clocks : clock name from clock manager

  - clock-names: must be main. It is the main clock of VPU

Optional properties:

  - memory-region: phandle to a node describing memory (see

    Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt)

    to be used for VPU extended memory; if not present, VPU may be located

    anywhere in the memory

Example:

	vpu: vpu@10020000 {

		compatible = "mediatek,mt8173-vpu";

		reg = <0 0x10020000 0 0x30000>,

		      <0 0x10050000 0 0x100>;

		reg-names = "tcm", "cfg_reg";

		interrupts = <GIC_SPI 166 IRQ_TYPE_LEVEL_HIGH>;

		clocks = <&topckgen TOP_SCP_SEL>;

		clock-names = "main";

	};