ieee802154: merge cleanup

A small cleanup after last net-2.6 merge into net-next-2.6

As we are going to free skb, no need to set skb->skb_iif or skb->dev

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>