drm/amdgpu: change how we update mmRLC_SPM_MC_CNTL

In pp_one_vf mode avoid the extra overhead and read/write the
registers without the KIQ.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Monk Liu <monk.liu@amd.com>
Acked-by: Yintian Tao <yintian.tao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>