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/isdn/i4l/isdn_net.c b/drivers/isdn/i4l/isdn_net.c
index 8209ed6..57bf4bf 100644
--- a/drivers/isdn/i4l/isdn_net.c
+++ b/drivers/isdn/i4l/isdn_net.c
@@ -1051,12 +1051,12 @@
 	isdn_net_dev *nd;
 	isdn_net_local *slp;
 	isdn_net_local *lp = (isdn_net_local *) netdev_priv(ndev);
-	int retv = 0;
+	int retv = NETDEV_TX_OK;
 
 	if (((isdn_net_local *) netdev_priv(ndev))->master) {
 		printk("isdn BUG at %s:%d!\n", __FILE__, __LINE__);
 		dev_kfree_skb(skb);
-		return 0;
+		return NETDEV_TX_OK;
 	}
 
 	/* For the other encaps the header has already been built */