[Why]
Adding support for Freesync HDMI to DC and DMCU

[How]
Create DC interface and implementation on top of DMCU to support
parsing CEA blocks in DMCU.
Signed-off-by: Stylon Wang <stylon.wang@amd.com>
Reviewed-by: Hersen Wu <hersenxs.wu@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>