drm/amdgpu/cz: enable/disable vce dpm even if vce pg is disabled

I missed this when cleaning up the vce pg handling.

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