tcp: fix SYN-data space mis-accounting

tcp: fix SYN-data space mis-accounting

[ Upstream commit 1b63edd6ecc55c3a61b40297b49e2323783bddfd ]

In fast open the sender unncessarily reduces the space available
for data in SYN by 12 bytes.  This is because in the sender
incorrectly reserves space for TS option twice in tcp_send_syn_data():
tcp_mtu_to_mss() already accounts for TS option space. But it further
reserves MAX_TCP_OPTION_SPACE when computing the payload space.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>