[SKB]: __skb_queue_after(prev) = __skb_insert(prev, prev->next)

By reordering, __skb_queue_after() is expressed in terms of __skb_insert().

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>