Freescale imx21 Framebuffer

This framebuffer driver supports devices imx1, imx21, imx25, and imx27.

Required properties:
- compatible : "fsl,<chip>-fb", chip should be imx1 or imx21
- reg : Should contain 1 register ranges(address and length)
- interrupts : One interrupt of the fb dev

Required nodes:
- display: Phandle to a display node as described in
	Documentation/devicetree/bindings/video/display-timing.txt
	Additional, the display node has to define properties:
	- bits-per-pixel: Bits per pixel
	- fsl,pcr: LCDC PCR value

Optional properties:
- lcd-supply: Regulator for LCD supply voltage.
- fsl,dmacr: DMA Control Register value. This is optional. By default, the
	register is not modified as recommended by the datasheet.
- fsl,lpccr: Contrast Control Register value. This property provides the
	default value for the contrast control register.
	If that property is ommited, the register is zeroed.
- fsl,lscr1: LCDC Sharp Configuration Register value.

Example:

	imxfb: fb@10021000 {
		compatible = "fsl,imx21-fb";
		interrupts = <61>;
		reg = <0x10021000 0x1000>;
		display = <&display0>;
	};

	...

	display0: display0 {
		model = "Primeview-PD050VL1";
		native-mode = <&timing_disp0>;
		bits-per-pixel = <16>;
		fsl,pcr = <0xf0c88080>;	/* non-standard but required */
		display-timings {
			timing_disp0: 640x480 {
				hactive = <640>;
				vactive = <480>;
				hback-porch = <112>;
				hfront-porch = <36>;
				hsync-len = <32>;
				vback-porch = <33>;
				vfront-porch = <33>;
				vsync-len = <2>;
				clock-frequency = <25000000>;
			};
		};
	};
