drm/amd/display: Enable CM low mem power optimization

[WHY & HOW]
MPC MCM low mem power optimization still causes color distortion on
first SCE enablement, only forces light sleep for it.

DPP low memory power optimization still needs this bit to save power.

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Yihan Zhu <yihan.zhu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>