TTY: use tty_wait_until_sent_from_close in tty_port_close_start

Let's use the newly added helper to avoid stalls in drivers which are
already ported to tty_port helpers.

We have to ensure here, that there is no user of tty_port_close_start
and tty_port_close which holds port->mutex (or other) lock over them.
And sure, there is none.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/tty/tty_port.c

@@ -350,7 +350,7 @@ int tty_port_close_start(struct tty_port *port,
 		tty_driver_flush_buffer(tty);
 	if (test_bit(ASYNCB_INITIALIZED, &port->flags) &&
 			port->closing_wait != ASYNC_CLOSING_WAIT_NONE)
-		tty_wait_until_sent(tty, port->closing_wait);
+		tty_wait_until_sent_from_close(tty, port->closing_wait);
 	if (port->drain_delay) {
 		unsigned int bps = tty_get_baud_rate(tty);
 		long timeout;