x25_asy: Fix ref count rule violation

x25_asy does not take an ldisc reference before calling the flush method.
Fix it to use the helper function we provide.
Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Krzysztof Halasa <khc@pm.waw.pl>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/net/wan/x25_asy.c

@@ -554,6 +554,7 @@ static void x25_asy_receive_buf(struct tty_struct *tty, const unsigned char *cp,
 static int x25_asy_open_tty(struct tty_struct *tty)
 {
 	struct x25_asy *sl = (struct x25_asy *) tty->disc_data;
+	struct tty_ldisc *ld;
 	int err;
 
 	/* First make sure we're not already connected. */
@@ -572,9 +573,7 @@ static int x25_asy_open_tty(struct tty_struct *tty)
 	if (tty->driver->flush_buffer)  {
 		tty->driver->flush_buffer(tty);
 	}
-	if (tty->ldisc.flush_buffer)  {
-		tty->ldisc.flush_buffer(tty);
-	}
+	tty_ldisc_flush(tty);
 
 	/* Restore default settings */
 	sl->dev->type = ARPHRD_X25;