[TCP]: Don't panic if S+L skb is detected

BUG_ON is an overkill. In fact, I was mislead by BUG_TRAP
severity (equals to WARN_ON) which is much lower than BUG_ON's
(that panics).
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -758,8 +758,8 @@ static inline __u32 tcp_current_ssthresh(const struct sock *sk)
 			    (tp->snd_cwnd >> 2)));
 }
 
-/* Use define here intentionally to get BUG_ON location shown at the caller */
-#define tcp_verify_left_out(tp)	BUG_ON(tcp_left_out(tp) > tp->packets_out)
+/* Use define here intentionally to get WARN_ON location shown at the caller */
+#define tcp_verify_left_out(tp)	WARN_ON(tcp_left_out(tp) > tp->packets_out)
 
 extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
 extern __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst);