XTENSA: iss/console, fix potential deadlock

If the timer ticks while we are holding the spinlock, the system
deadlocks. It is due to synchronous del_timer.

So to fix that, use spinlocks that properly disable bottom halves.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/xtensa/platforms/iss/console.c

@@ -91,11 +91,10 @@ static int rs_open(struct tty_struct *tty, struct file * filp)
  */
 static void rs_close(struct tty_struct *tty, struct file * filp)
 {
-	spin_lock(&timer_lock);
+	spin_lock_bh(&timer_lock);
 	if (tty->count == 1)
-		/* this will cause a deadlock if the timer ticks right now */
 		del_timer_sync(&serial_timer);
-	spin_unlock(&timer_lock);
+	spin_unlock_bh(&timer_lock);
 }