drm/amd/display: unblock mcm_luts

why and how:
needed to fix bad assumption for enable mcm_luts

Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Martin Leung <Martin.Leung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>