drm/amd/powerplay: enable UMDPSTATE support on raven2 (v2)

enable UMDPSTATE support to force performance level for raven2.

v2: squash in warning fix (Alex)

Signed-off-by: Chengming Gui <Jack.Gui@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>