drm/amdgpu: Complete multimedia bandwidth interface

- Update SRIOV PF2VF header with latest revision

- Extend existing function in amdgpu_virt.c to read MM bandwidth config
  from PF2VF message

- Add SRIOV Sienna Cichlid codec array and update the bandwidth with
  PF2VF message

v2: squash in removal of unused variable (Alex)

Signed-off-by: Bokun Zhang <bokun.zhang@amd.com>
Reviewed-by: Monk liu <monk.liu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>