niu: VLAN_ETH_HLEN should be used to make sure that the whole MAC header was...

niu: VLAN_ETH_HLEN should be used to make sure that the whole MAC header was copied to the head buffer in the Vlan packets case

Signed-off-by: Joyce Yu <joyce.yu@sun.com>
Signed-off-by: David S. Miller <davem@davemloft.net>