Add support for the B and C planes which support RGB and YUV pixel
formats and can be used as overlays or hardware cursor. Currently 32-bit
XRGB as well as UYVY, YUV420 and YUV422 pixel formats are advertised.
Other formats should be easy to add but these are the most common ones
and should cover the majority of use-cases.
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>