drm/amd/display: Add DC interface for custom CSC matrix

Signed-off-by: Yue Hin Lau <Yuehin.Lau@amd.com>
Reviewed-by: Vitaly Prosyak <Vitaly.Prosyak@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>