IEEE 802.1Q says that when we receive priority-tagged (VID 0) frames
use the PVID for the port as its VID.
(See IEEE 802.1Q-2011 6.9.1 and Table 9-2)

Apply the PVID to not only untagged frames but also priority-tagged frames.
Signed-off-by: NToshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Reviewed-by: NVlad Yasevich <vyasevic@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>