The supported set of color modes varies for different DISPC pipelines(plane)
and omap version. This makes the checks for validation of a color mode more
complicated as new omap versions are added.

A dss_feature function is created which tells if a color_mode is supported
for a plane on the current omap revision.
Signed-off-by: NArchit Taneja <archit@ti.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@nokia.com>