TTY: add tty_port_tty_hangup helper

It allows for cleaning up on a considerable amount of places. They did
port_get, hangup, kref_put. Now the only thing needed is to call
tty_port_tty_hangup which does exactly that. And they can also decide
whether to consider CLOCAL or completely ignore that.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/nozomi.c

@@ -1501,12 +1501,9 @@ static void tty_exit(struct nozomi *dc)
 
 	DBG1(" ");
 
-	for (i = 0; i < MAX_PORT; ++i) {
-		struct tty_struct *tty = tty_port_tty_get(&dc->port[i].port);
-		if (tty && list_empty(&tty->hangup_work.entry))
-			tty_hangup(tty);
-		tty_kref_put(tty);
-	}
+	for (i = 0; i < MAX_PORT; ++i)
+		tty_port_tty_hangup(&dc->port[i].port, false);
+
 	/* Racy below - surely should wait for scheduled work to be done or
 	   complete off a hangup method ? */
 	while (dc->open_ttys)