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/farsync.c b/drivers/net/wan/farsync.c
index 90c0a31..20a1237 100644
--- a/drivers/net/wan/farsync.c
+++ b/drivers/net/wan/farsync.c
@@ -2294,7 +2294,7 @@
 		dbg(DBG_ASS,
 		    "Tried to transmit but no carrier on card %d port %d\n",
 		    card->card_no, port->index);
-		return 0;
+		return NETDEV_TX_OK;
 	}
 
 	/* Drop it if it's too big! MTU failure ? */
@@ -2303,7 +2303,7 @@
 		    LEN_TX_BUFFER);
 		dev_kfree_skb(skb);
 		dev->stats.tx_errors++;
-		return 0;
+		return NETDEV_TX_OK;
 	}
 
 	/*
@@ -2337,7 +2337,7 @@
 		dev->stats.tx_errors++;
 		dbg(DBG_ASS, "Tx queue overflow card %d port %d\n",
 		    card->card_no, port->index);
-		return 0;
+		return NETDEV_TX_OK;
 	}
 
 	/*
@@ -2354,7 +2354,7 @@
 	fst_q_work_item(&fst_work_txq, card->card_no);
 	tasklet_schedule(&fst_tx_task);
 
-	return 0;
+	return NETDEV_TX_OK;
 }
 
 /*