net: convert remaining non-symbolic return values in ndo_start_xmit() functions

This patch converts the remaining occurences of raw return values to their
symbolic counterparts in ndo_start_xmit() functions that were missed by the
previous automatic conversion.

Additionally code that assumed the symbolic value of NETDEV_TX_OK to be zero
is changed to explicitly use NETDEV_TX_OK.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/wan/dlci.c b/drivers/net/wan/dlci.c
index 2fa275a..8526b6d 100644
--- a/drivers/net/wan/dlci.c
+++ b/drivers/net/wan/dlci.c
@@ -194,7 +194,7 @@
 	ret = 0;
 
 	if (!skb || !dev)
-		return(0);
+		return NETDEV_TX_OK;
 
 	dlp = netdev_priv(dev);
 
@@ -219,7 +219,7 @@
 	/* Alan Cox recommends always returning 0, and always freeing the packet */
 	/* experience suggest a slightly more conservative approach */
 
-	if (!ret)
+	if (ret == NETDEV_TX_OK)
 	{
 		dev_kfree_skb(skb);
 		netif_wake_queue(dev);