tty: add throttle/unthrottle helpers

Something Arjan suggested which allows us to clean up the code nicely

Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index a6c2619..e5cd856 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -370,9 +370,7 @@
 	hu->hdev->stat.byte_rx += count;
 	spin_unlock(&hu->rx_lock);
 
-	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
-					tty->ops->unthrottle)
-		tty->ops->unthrottle(tty);
+	tty_unthrottle(tty);
 }
 
 static int hci_uart_register_dev(struct hci_uart *hu)