drm: mali-dp: Add YUV->RGB conversion support for video layers

Internally Mali DP uses an RGB pipeline so video layers that support
YUV input buffers need to convert the input data to RGB. The YUV
buffers can have various encodings and this patch introduces support
for BT.601, BT.709 and BT.2020 encodings, both limited and full ranges.

This patch adds support for specifying the color encoding of the
input buffers for the planes that are backed by the video layers
and programs the YUV2RGB coefficients into hardware based on the
selected encoding.

Signed-off-by: Mihail Atanassov <mihail.atanassov@arm.com>
[updated to use standard properties]
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>