drm/amd/display: copy dmub caps to dc on dcn31

[Why & How]
Add code path to copy dmub caps to dc, which is missing on dcn31

Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Josip Pavic <Josip.Pavic@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>