drm/amdgpu:two fixings for sdma v4 for SRIOV

no hw_fini for SRIOV, otherwise other VF will be affected
no CG for SRIOV

Signed-off-by: Monk Liu <Monk.Liu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>