drm/amdgpu: Power on uvd block when hw_fini

when hw_fini/suspend, smu only need to power on uvd block
if uvd pg is supported, don't need to call uvd to do hw_init.

v2: fix typo in patch descriptions and comments.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Tested-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>