drm/amd/powerplay: add uvd/vce dpm enabling flag default.

These should be set by default otherwise the UVD/VCE performance
won't be optimal.

Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>