drm/amdgpu: skip "Issue additional private vm invalidation to MMHUB" on SRIOV

[Why]
vm_l2_bank_select_reserved_cid2 is a PF_only register
that cannot be programmed by VF. This feature is only
support HDP using GPUVM page tables to access FB memory
which should be disabled on SRIOV.

[How]
Disable the feature on VF.

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Yifan Zha <Yifan.Zha@amd.com>
Signed-off-by: Horace Chen <horace.chen@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>