tcp: clear tp->segs_{in|out} in tcp_disconnect()

tp->segs_in and tp->segs_out need to be cleared in tcp_disconnect().

tcp_disconnect() is rarely used, but it is worth fixing it.

Fixes: 2efd055c ("tcp: add tcpi_segs_in and tcpi_segs_out to tcp_info")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Marcelo Ricardo Leitner <mleitner@redhat.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>