gianfar: use netif_tx_queue_stopped instead of __netif_subqueue_stopped

The __netif_subqueue_stopped() just does the following:

        struct netdev_queue *txq = netdev_get_tx_queue(dev, queue_index);
        return netif_tx_queue_stopped(txq);

and since we already have the txq in scope, we can just call that
directly in this case.
Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

drivers/net/ethernet/freescale/gianfar.c

@@ -2565,7 +2565,7 @@ static int gfar_clean_tx_ring(struct gfar_priv_tx_q *tx_queue)
 	}
 
 	/* If we freed a buffer, we can restart transmission, if necessary */
-	if (__netif_subqueue_stopped(dev, tqi) && tx_queue->num_txbdfree)
+	if (netif_tx_queue_stopped(txq) && tx_queue->num_txbdfree)
 		netif_wake_subqueue(dev, tqi);
 
 	/* Update dirty indicators */