net: sonic: return NETDEV_TX_OK if failed to map buffer

NETDEV_TX_BUSY really should only be used by drivers that call
netif_tx_stop_queue() at the wrong moment. If dma_map_single() is
failed to map tx DMA buffer, it might trigger an infinite loop.
This patch use NETDEV_TX_OK instead of NETDEV_TX_BUSY, and change
printk to pr_err_ratelimited.

Fixes: d9fb9f38 ("*sonic/natsemi/ns83829: Move the National Semi-conductor drivers")
Signed-off-by: Mao Wenan <maowenan@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/natsemi/sonic.c

@@ -232,9 +232,9 @@ static int sonic_send_packet(struct sk_buff *skb, struct net_device *dev)
 
 	laddr = dma_map_single(lp->device, skb->data, length, DMA_TO_DEVICE);
 	if (!laddr) {
-		printk(KERN_ERR "%s: failed to map tx DMA buffer.\n", dev->name);
+		pr_err_ratelimited("%s: failed to map tx DMA buffer.\n", dev->name);
 		dev_kfree_skb(skb);
-		return NETDEV_TX_BUSY;
+		return NETDEV_TX_OK;
 	}
 
 	sonic_tda_put(dev, entry, SONIC_TD_STATUS, 0);       /* clear status */