net: bcmgenet: cleanup for bcmgenet_xmit()

1. Readability: Move nr_frags assignment a few lines down in order
   to bundle index -> ring -> txq calculations together.
2. Readability: Add parentheses around nr_frags + 1.
3. Minor fix: Stop the Tx queue and throw the error message only if
   the Tx queue hasn't already been stopped.

Signed-off-by: Petri Gynther <pgynther@google.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/genet/bcmgenet.c

@@ -1447,15 +1447,19 @@ static netdev_tx_t bcmgenet_xmit(struct sk_buff *skb, struct net_device *dev)
 	else
 		index -= 1;
 
-	nr_frags = skb_shinfo(skb)->nr_frags;
 	ring = &priv->tx_rings[index];
 	txq = netdev_get_tx_queue(dev, ring->queue);
 
+	nr_frags = skb_shinfo(skb)->nr_frags;
+
 	spin_lock_irqsave(&ring->lock, flags);
-	if (ring->free_bds <= nr_frags + 1) {
-		netif_tx_stop_queue(txq);
-		netdev_err(dev, "%s: tx ring %d full when queue %d awake\n",
-			   __func__, index, ring->queue);
+	if (ring->free_bds <= (nr_frags + 1)) {
+		if (!netif_tx_queue_stopped(txq)) {
+			netif_tx_stop_queue(txq);
+			netdev_err(dev,
+				   "%s: tx ring %d full when queue %d awake\n",
+				   __func__, index, ring->queue);
+		}
 		ret = NETDEV_TX_BUSY;
 		goto out;
 	}