pty: Remove redundant itty reset

port->itty has already been reset by release_tty() before
pty_cleanup() is called.

Call stack:
release_tty()
  tty_kref_put()
    queue_release_one_tty()
      release_one_tty() : workqueue
        tty->ops->cleanup()
          pty_cleanup()

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/pty.c

@@ -413,7 +413,6 @@ static void pty_unix98_shutdown(struct tty_struct *tty)
 
 static void pty_cleanup(struct tty_struct *tty)
 {
-	tty->port->itty = NULL;
 	tty_port_put(tty->port);
 }