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>

drivers/net/hamradio/6pack.c

@@ -491,9 +491,7 @@ static void sixpack_receive_buf(struct tty_struct *tty,
 	sixpack_decode(sp, buf, count1);
 
 	sp_put(sp);
-	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
-	    && tty->ops->unthrottle)
-		tty->ops->unthrottle(tty);
+	tty_unthrottle(tty);
 }
 
 /*