vdpa: Restore vlan filtering state

This patch introduces vhost_vdpa_net_load_single_vlan()
and vhost_vdpa_net_load_vlan() to restore the vlan
filtering state at device's startup.

Co-developed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Hawkins Jiawei <yin31149@gmail.com>
Message-Id: <e76a29f77bb3f386e4a643c8af94b77b775d1752.1690106284.git.yin31149@gmail.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>