drm/amdgpu: not set cg for vce/uvd in late init.

no need to set cg for uvd/vce in late init.
As when ring test, uvd/vce's dpm will be enabled/disabled.
the cg will be set.

fix issue suspend when play video or encode, then resume back,
the clock will be bypassed on Polaris/Fiji.

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>