net: add data-race annotations in softnet_seq_show()

softnet_seq_show() reads several fields that might be updated
concurrently. Add READ_ONCE() and WRITE_ONCE() annotations.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250407163602.170356-4-edumazet@google.com


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