irtty-sir.c: Do not set_termios() on irtty_close()

Issuing set_termios() from irtty_close() causes kernel Oops for
unplugged usb-serial devices.

Since no other tty_ldisc calls set_termios() on close and no tty driver
seem to check if tty->device_data is NULL or not on entry to set_termios(),
the only solution I can come up with is to remove the irtty_stop_receiver()
call, which only updates termios.
Signed-off-by: NTommie Gannert <tommie@gannert.se>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/irda/irtty-sir.c

@@ -522,7 +522,6 @@ static void irtty_close(struct tty_struct *tty)
 	sirdev_put_instance(priv->dev);
 
 	/* Stop tty */
-	irtty_stop_receiver(tty, TRUE);
 	clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 	if (tty->ops->stop)
 		tty->ops->stop(tty);