HDMI deep color setup must know which modes are supported if
it needs to degrade gracefully, as only 12 bpc / dc_36 is
guaranteed, but 10 bpc / dc_30 is optional. The maximum bpc
is not sufficient for this.
Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>