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/wireless/ipw2x00/libipw_tx.c b/drivers/net/wireless/ipw2x00/libipw_tx.c
index da2ad54..2e8f84f 100644
--- a/drivers/net/wireless/ipw2x00/libipw_tx.c
+++ b/drivers/net/wireless/ipw2x00/libipw_tx.c
@@ -527,13 +527,13 @@
 		if (ret == 0) {
 			dev->stats.tx_packets++;
 			dev->stats.tx_bytes += txb->payload_size;
-			return 0;
+			return NETDEV_TX_OK;
 		}
 
 		ieee80211_txb_free(txb);
 	}
 
-	return 0;
+	return NETDEV_TX_OK;
 
       failed:
 	spin_unlock_irqrestore(&ieee->lock, flags);