[Why]
By default we shouldn't be trying to write secure registers during
DMUB hardware init.

[How]
Add a parameter to control whether we put the DMCUB into secure reset
and attempt to load CW0/CW1.
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>