drm/amd/display: Add misc DC changes for DCN401

Add miscellaneous changes to enable DCN401 init

Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>