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>
diff --git a/arch/um/drivers/chan_kern.c b/arch/um/drivers/chan_kern.c
index 15c553c..bf42825 100644
--- a/arch/um/drivers/chan_kern.c
+++ b/arch/um/drivers/chan_kern.c
@@ -568,11 +568,7 @@
 		reactivate_fd(chan->fd, irq);
 	if (err == -EIO) {
 		if (chan->primary) {
-			struct tty_struct *tty = tty_port_tty_get(&line->port);
-			if (tty != NULL) {
-				tty_hangup(tty);
-				tty_kref_put(tty);
-			}
+			tty_port_tty_hangup(&line->port, false);
 			if (line->chan_out != chan)
 				close_one_chan(line->chan_out, 1);
 		}