tty: n_gsm: fix wrong DLCI release order

tty: n_gsm: fix wrong DLCI release order

commit 3d8c9b003a23c5a2fb0953a17b20eec8f895691b upstream.

The current DLCI release order starts with the control channel followed by
the user channels. Reverse this order to keep the control channel open
until all user channels have been released.

Fixes: 99551fa31543 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-9-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>