igb: add VF trust infrastructure

* Add a per-VF value to know if a VF is trusted, by default don't
  trust VFs.

* Implement netdev op to trust VFs (igb_ndo_set_vf_trust) and add
  trust status to ndo_get_vf_config output.

* Allow a trusted VF to change MAC and MAC filters even if MAC
  has been administratively set.

Signed-off-by: Corinna Vinschen <vinschen@redhat.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>