This field can be read locklessly.

Fixes: 1536e285 ("tcp: Add a TCP_FASTOPEN socket option to get a max backlog on its listner")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20230719212857.3943972-12-edumazet@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>