Add a standard optional properties to support different non RGB color
encodings in DRM planes. COLOR_ENCODING select the supported non RGB
color encoding, for instance ITU-R BT.709 YCbCr. COLOR_RANGE selects
the value ranges within the selected color encoding. The properties
are stored to drm_plane object to allow different set of supported
encoding for different planes on the device.

v2: Add/fix kerneldocs, verify bitmasks (danvet)

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Daniel Stone <daniel@fooishbar.org>
Cc: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Uma Shankar <uma.shankar@intel.com>
Cc: Shashank Sharma <shashank.sharma@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jyri Sarha <jsarha@ti.com>
[vsyrjala v2: Add/fix kerneldocs, verify bitmasks]
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180219202823.10508-1-ville.syrjala@linux.intel.comAcked-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>