drm/amd/display: Skip powerstate DC hw access if virtual dal

[Why]
On baco-enabled systems running virtual dal, can get set power
state when hw is not initialized

[How]
Skip DC hw part of setPowerState when hw not available

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Martin Leung <martin.leung@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Eryk Brol <eryk.brol@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>