No lock protects tcp tw fields.

tcptw->tw_rcv_nxt can be changed from twsk_rcv_nxt_update()
while other threads might read this field.

Add READ_ONCE()/WRITE_ONCE() annotations, and make sure
tcp_timewait_state_process() reads tcptw->tw_rcv_nxt only once.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Link: https://patch.msgid.link/20240827015250.3509197-3-edumazet@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>