Revert "tty:n_gsm.c: destroy port by tty_port_destroy()"

This reverts commit 7726fb53.

Jiri writes:
	On 24. 09. 19, 11:25, Xiaoming Ni wrote:
	> According to the comment of tty_port_destroy():
	>     When a port was initialized using tty_port_init, one has to destroy
	>     the port by tty_port_destroy();

	It continues with a part saying:
	   Either indirectly by using tty_port refcounting
	   (tty_port_put) or directly if refcounting is not used.

So this should be reverted.

Cc: Xiaoming Ni <nixiaoming@huawei.com>
Reported-by: Jiri Slaby <jslaby@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/n_gsm.c

@@ -1681,7 +1681,6 @@ static void gsm_dlci_free(struct tty_port *port)
 
 	del_timer_sync(&dlci->t1);
 	dlci->gsm->dlci[dlci->addr] = NULL;
-	tty_port_destroy(&dlci->port);
 	kfifo_free(dlci->fifo);
 	while ((dlci->skb = skb_dequeue(&dlci->skb_list)))
 		dev_kfree_skb(dlci->skb);