net: use symbolic values for ndo_start_xmit() return codes

Convert magic values 1 and -1 to NETDEV_TX_BUSY and NETDEV_TX_LOCKED respectively.

0 (NETDEV_TX_OK) is not changed to keep the noise down, except in very few cases
where its in direct proximity to one of the other values.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/tlan.c b/drivers/net/tlan.c
index aa69649..384cb5e 100644
--- a/drivers/net/tlan.c
+++ b/drivers/net/tlan.c
@@ -1111,7 +1111,7 @@
 			  dev->name, priv->txHead, priv->txTail );
 		netif_stop_queue(dev);
 		priv->txBusyCount++;
-		return 1;
+		return NETDEV_TX_BUSY;
 	}
 
 	tail_list->forward = 0;