vlan: fix vlan_skb_recv()

Bruno Prémont found commit 9793241f


(vlan: Precise RX stats accounting) added a regression for non
hw accelerated vlans.

[   26.390576] BUG: unable to handle kernel NULL pointer dereference at (null)
[   26.396369] IP: [<df856b89>] vlan_skb_recv+0x89/0x280 [8021q]

vlan_dev_info() was used with original device, instead of
skb->dev. Also spotted by Américo Wang.

Reported-By: Bruno Prémont <bonbons@linux-vserver.org>
Tested-By: Bruno Prémont <bonbons@linux-vserver.org>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>