video: vt8500: Add devicetree support for vt8500-fb and wm8505-fb

Update vt8500-fb, wm8505-fb and wmt-ge-rops to support device
tree bindings.
Small change in wm8505-fb.c to support WM8650 framebuffer color
format.

Signed-off-by: Tony Prisk <linux@prisktech.co.nz>