tcp: use tcp_jiffies32 to feed tp->snd_cwnd_stamp

Use tcp_jiffies32 instead of tcp_time_stamp to feed
tp->snd_cwnd_stamp.

tcp_time_stamp will soon be a litle bit more expensive
than simply reading 'jiffies'.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 653bbd6..102b2c9 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -524,7 +524,7 @@
 		tp->snd_cwnd = 1;
 	else
 		tp->snd_cwnd = tcp_init_cwnd(tp, dst);
-	tp->snd_cwnd_stamp = tcp_time_stamp;
+	tp->snd_cwnd_stamp = tcp_jiffies32;
 }
 
 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst)