[TCP]: Kill warning in tcp_clean_rtx_queue().

GCC can't tell we always initialize 'tv' in all the cases
we actually use it, so explicitly set it up with zeros.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

@@ -2259,7 +2259,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
 	u32 pkts_acked = 0;
 	void (*rtt_sample)(struct sock *sk, u32 usrtt)
 		= icsk->icsk_ca_ops->rtt_sample;
-	struct timeval tv;
+	struct timeval tv = { .tv_sec = 0, .tv_usec = 0 };
 
 	while ((skb = skb_peek(&sk->sk_write_queue)) &&
 	       skb != sk->sk_send_head) {