lcd: add functions to set up simplefb device tree

simple-framebuffer is a new device tree binding that describes a pre-
configured frame-buffer memory region and its format. The Linux kernel
contains a driver that supports this binding. Implement functions to
create a DT node (or fill in an existing node) with parameters that
describe the framebuffer format that U-Boot is using.

This will be immediately used by the Raspberry Pi board in U-Boot, and
likely will be used by the Samsung ARM ChromeBook support soon too. It
could well be used by many other boards (e.g. Tegra boards with built-in
LCD panels, which aren't yet supported by the Linux kernel).

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Simon Glass <sjg@chromium.org>

doc/device-tree-bindings/video/simple-framebuffer.txt

@@ -0,0 +1,25 @@
+Simple Framebuffer
+
+A simple frame-buffer describes a raw memory region that may be rendered to,
+with the assumption that the display hardware has already been set up to scan
+out from that buffer.
+
+Required properties:
+- compatible: "simple-framebuffer"
+- reg: Should contain the location and size of the framebuffer memory.
+- width: The width of the framebuffer in pixels.
+- height: The height of the framebuffer in pixels.
+- stride: The number of bytes in each line of the framebuffer.
+- format: The format of the framebuffer surface. Valid values are:
+  - r5g6b5 (16-bit pixels, d[15:11]=r, d[10:5]=g, d[4:0]=b).
+
+Example:
+
+	framebuffer {
+		compatible = "simple-framebuffer";
+		reg = <0x1d385000 (1600 * 1200 * 2)>;
+		width = <1600>;
+		height = <1200>;
+		stride = <(1600 * 2)>;
+		format = "r5g6b5";
+	};