[media] bdisp: add DT bindings documentation

STMicroelectronics stih4xx platforms

bdisp: 2D blitter for STMicroelectronics SoC.

Required properties:

- compatible: should be "st,stih407-bdisp".

- reg: BDISP physical address location and length.

- interrupts: BDISP interrupt number.

- clocks: from common clock binding: handle hardware IP needed clocks, the

  number of clocks may depend on the SoC type.

  See ../clocks/clock-bindings.txt for details.

- clock-names: names of the clocks listed in clocks property in the same order.

Example:

	bdisp0:bdisp@9f10000 {

		compatible = "st,stih407-bdisp";

		reg = <0x9f10000 0x1000>;

		interrupts = <GIC_SPI 38 IRQ_TYPE_NONE>;

		clock-names = "bdisp";

		clocks = <&clk_s_c0_flexgen CLK_IC_BDISP_0>;

	};

Aliases:

Each BDISP should have a numbered alias in the aliases node, in the form of

bdispN, N = 0 or 1.

Example:

	aliases {

		bdisp0 = &bdisp0;

	};