Revert "ipv4: tcp: dont cache unconfirmed intput dst"

This reverts commit c074da2810c118b3812f32d6754bd9ead2f169e7.

This change has several unwanted side effects:

1) Sockets will cache the DST_NOCACHE route in sk->sk_rx_dst and we'll
   thus never create a real cached route.

2) All TCP traffic will use DST_NOCACHE and never use the routing
   cache at all.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 917ed2e..6660ffc 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -325,7 +325,7 @@
 
 extern void tcp_shutdown (struct sock *sk, int how);
 
-extern int tcp_v4_early_demux(struct sk_buff *skb, bool *nocache);
+extern int tcp_v4_early_demux(struct sk_buff *skb);
 extern int tcp_v4_rcv(struct sk_buff *skb);
 
 extern struct inet_peer *tcp_v4_get_peer(struct sock *sk);