drm/amd/display: Add debug option for disabling SLDO optimizations

[Why]
DM can hook this up to disable SLDO optimizations in firmware during
DMCUB initialization for debug purposes.

[How]
Add the option and pass it through dmub_srv.

Reviewed-by: Hansen Dsouza <hansen.dsouza@amd.com>
Signed-off-by: Jerry Zuo <jerry.zuo@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>