drm/amd/display: [backport] dwb dm + efc support

dwb fixes.

Signed-off-by: Charlene Liu <charlene.liu@amd.com>
Reviewed-by: Duke Du <Duke.Du@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>