Enable UVD dpm (dynamic power management) and powergating.  UVD dpm dynamically scales the UVD
clocks on demand.  Powergating turns off the power to the block when it's not in use.
Signed-off-by: NSonny Jiang <sonny.jiang@amd.com>
Acked-by: NChristian König <christian.koenig@amd.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>