tcp: Don't set treq->req_usec_ts in cookie_tcp_reqsk_init().

tcp: Don't set treq->req_usec_ts in cookie_tcp_reqsk_init().

Commit de5626b95e13 ("tcp: Factorise cookie-independent fields
initialisation in cookie_v[46]_check().") miscategorised
tcp_rsk(req)->req_usec_ts init to cookie_tcp_reqsk_init(),
which is used by both BPF/non-BPF SYN cookie reqsk.

Rather, it should have been moved to cookie_tcp_reqsk_alloc() by
commit 8e7bab6b9652 ("tcp: Factorise cookie-dependent fields
initialisation in cookie_v[46]_check()") so that only non-BPF SYN
cookie sets tcp_rsk(req)->req_usec_ts to false.

Let's move the initialisation to cookie_tcp_reqsk_alloc() to
respect bpf_tcp_req_attrs.usec_ts_ok.

Fixes: e472f88891ab ("bpf: tcp: Support arbitrary SYN Cookie.")
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260410235328.1773449-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>