tty: n_gsm: Save dlci address open status when config requester

tty: n_gsm: Save dlci address open status when config requester

[ Upstream commit 0b91b5332368f2fb0c3e5cfebc6aff9e167acd8b ]

When n_gsm config "initiator=0",as requester ,receive SABM frame,n_gsm
register gsmtty dev,and save dlci open address status,if receive DLC0
DISC or CLD frame,it can unregister the gsmtty dev by saving dlci address.

Signed-off-by: Zhenguo Zhao <Zhenguo.Zhao1@unisoc.com>
Link: https://lore.kernel.org/r/1629461872-26965-8-git-send-email-zhenguo6858@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>