Simple display panel

Required properties:
- power-supply: regulator to provide the supply voltage

Optional properties:
- compatible: value maybe one of the following
		"simple-panel";
		"simple-panel-dsi";

- ddc-i2c-bus: phandle of an I2C controller used for DDC EDID probing
- enable-gpios: GPIO pin to enable or disable the panel
- backlight: phandle of the backlight device attached to the panel

Required properties when compatible is "simple-panel" or "simple-panel-dsi":
- display-timings: see display-timing.txt for information

Optional properties when compatible is a dsi devices:
- dsi,flags: dsi operation mode related flags
- dsi,format: pixel format for video mode
- dsi,lanes: number of active data lanes
- reset-gpios: GPIO pin to reset the panel
- reset-delay-ms: reset pulse width
- panel-init-sequence: A byte stream formed by simple multiple dcs packets.
	byte 0: dcs data type
	byte 1: wait number of specified ms after dcs command transmitted
	byte 2, 3: 16 bits length in network byte order
	byte 4 and beyond: number byte of payload
- panel-exit-sequence: A byte stream formed by simple multiple dcs packets.
	byte 0: dcs data type
	byte 1: wait number of specified ms after dcs command transmitted
	byte 2, 3: 16 bits length in network byte order
	byte 4 and beyond: number byte of payload

Example:

	panel: panel {
		compatible = "cptt,claa101wb01";
		ddc-i2c-bus = <&panelddc>;

		power-supply = <&vdd_pnl_reg>;
		enable-gpios = <&gpio 90 0>;

		backlight = <&backlight>;
	};

Or:
	panel: panel {
		compatible = "simple-panel-dsi";
		ddc-i2c-bus = <&panelddc>;

		power-supply = <&vdd_pnl_reg>;
		enable-gpios = <&gpio 90 0>;

		reset-gpios = <&gpio 91 0>;
		reset-delay-ms = <20>;

		backlight = <&backlight>;

		dsi,flags = <MIPI_DSI_MODE_VIDEO |
			     MIPI_DSI_MODE_VIDEO_BURST |
			     MIPI_DSI_MODE_VIDEO_SYNC_PULSE>;
		dsi,format = <MIPI_DSI_FMT_RGB888>;
		dsi,lanes = <4>;

		panel-init-sequence = [
			39 00 00 10 b1 6c 15 15 24 E4 11 f1 80 e4
				    d7 23 80 c0 d2 58
			...
			05 78 00 01 11
			05 00 00 01 29
		];

		panel-exit-sequence = [
			05 00 00 01 28
			05 78 00 01 10
		];

		display-timings {
			native-mode = <&timing0>;
			timing0: timing0 {
				clock-frequency = <160000000>;
				hactive = <1200>;
				vactive = <1920>;
				hback-porch = <21>;
				hfront-porch = <120>;
				vback-porch = <18>;
				vfront-porch = <21>;
				hsync-len = <20>;
				vsync-len = <3>;
				hsync-active = <0>;
				vsync-active = <0>;
				de-active = <0>;
				pixelclk-active = <0>;
			};
		};
	};