[8139TOO]: Use rtnl_lock_interruptible()

The 8139too thread needs to use rtnl_lock_interruptible so it can avoid
doing the actual work once it's been kill_proc()ed on module removal
time.

Based on debugging and an earlier patch that adds a driver-private
semaphore from Herbert Xu.
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/8139too.c

@@ -1636,7 +1636,8 @@ static int rtl8139_thread (void *data)
 		if (tp->time_to_die)
 			break;
 
-		rtnl_lock ();
+		if (rtnl_lock_interruptible ())
+			break;
 		rtl8139_thread_iter (dev, tp, tp->mmio_addr);
 		rtnl_unlock ();
 	}