sandbox: Support changing the LCD colour depth

Add a new device-tree property to control the colour depth. At present we
support 16bpp and 32bpp.

While we are here, update the code to use livetree.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Anatolij Gustschin <agust@denx.de>
3 files changed