[Why]
Regamma/CTM tests require CRC support

[How]
The CRC registers that were used in DCE exist under different
names in DCN.  The code was copied from DCE (in
dc/dce110/dce110_timing_generator.c) into DCN, and changed to
use the DCN register access helper functions.
Signed-off-by: David Francis <David.Francis@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>