net: atm: fix /proc/net/atm/lec handling

/proc/net/atm/lec must ensure safety against dev_lec[] changes.

It appears it had dev_put() calls without prior dev_hold(),
leading to imbalance and UAF.

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Francois Romieu <romieu@fr.zoreil.com> # Minor atm contributor
Link: https://patch.msgid.link/20250618140844.1686882-3-edumazet@google.com


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