[NET]: Kill skb->list

Remove the "list" member of struct sk_buff, as it is entirely
redundant.  All SKB list removal callers know which list the
SKB is on, so storing this in sk_buff does nothing other than
taking up some space.

Two tricky bits were SCTP, which I took care of, and two ATM
drivers which Francois Romieu <romieu@fr.zoreil.com> fixed
up.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>

net/ax25/ax25_subr.c

@@ -76,7 +76,7 @@ void ax25_requeue_frames(ax25_cb *ax25)
 		if (skb_prev == NULL)
 			skb_queue_head(&ax25->write_queue, skb);
 		else
-			skb_append(skb_prev, skb);
+			skb_append(skb_prev, skb, &ax25->write_queue);
 		skb_prev = skb;
 	}
 }