vlan: use struct netdev_queue counters instead of dev->stats

We can update netdev_queue tx_bytes/tx_packets/tx_dropped counters instead
of dev->stats ones, to reduce number of cache lines dirtied in xmit path.

This fixes a performance problem on SMP when many different cpus take
vlan tx path.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>