tcp: do not clear srtt_us in tcp_create_openreq_child

All listeners have this field cleared already, since tcp_disconnect()
clears it and newly created sockets have also a zero value here.

So a clone will inherit a zero value here.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_minisocks.c

@@ -479,7 +479,6 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
 
 	tcp_init_wl(newtp, treq->rcv_isn);
 
-	newtp->srtt_us = 0;
 	newtp->mdev_us = jiffies_to_usecs(TCP_TIMEOUT_INIT);
 	minmax_reset(&newtp->rtt_min, tcp_jiffies32, ~0U);
 	newicsk->icsk_ack.lrcvtime = tcp_jiffies32;