tcp: annotate data-races in tcp_req_diag_fill()

req->num_retrans and rsk_timer.expires are read locklessly,
and can be changed from tcp_rtx_synack().

Add READ_ONCE()/WRITE_ONCE() annotations.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250828102738.2065992-3-edumazet@google.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>