[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/ipv4/tcp.c

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 69b1fcf..d2696af 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -975,7 +975,7 @@
 	if (!skb->len) {
 		if (sk->sk_send_head == skb)
 			sk->sk_send_head = NULL;
-		__skb_unlink(skb, skb->list);
+		__skb_unlink(skb, &sk->sk_write_queue);
 		sk_stream_free_skb(sk, skb);
 	}