This patch enables detecting VCE/UVD PG features and fixes the
UVD powergate function.

Tested on a Tonga (by reading UVD tile/clk bits during playback/idle).
Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>