Doc/DT: Add DT binding documentation for MIPI DPI Panel

Generic MIPI DPI Panel

======================

Required properties:

- compatible: "panel-dpi"

Optional properties:

- label: a symbolic name for the panel

- enable-gpios: panel enable gpio

Required nodes:

- "panel-timing" containing video timings

  (Documentation/devicetree/bindings/video/display-timing.txt)

- Video port for DPI input

Example

-------

lcd0: display@0 {

        compatible = "samsung,lte430wq-f0c", "panel-dpi";

        label = "lcd";

        port {

            lcd_in: endpoint {

                    remote-endpoint = <&dpi_out>;

            };

        };

        panel-timing {

                clock-frequency = <9200000>;

                hactive = <480>;

                vactive = <272>;

                hfront-porch = <8>;

                hback-porch = <4>;

                hsync-len = <41>;

                vback-porch = <2>;

                vfront-porch = <4>;

                vsync-len = <10>;

                hsync-active = <0>;

                vsync-active = <0>;

                de-active = <1>;

                pixelclk-active = <1>;

        };

};