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/mace.c b/drivers/net/mace.c
index 1ad740b..1427755 100644
--- a/drivers/net/mace.c
+++ b/drivers/net/mace.c
@@ -547,7 +547,7 @@
 	netif_stop_queue(dev);
 	mp->tx_fullup = 1;
 	spin_unlock_irqrestore(&mp->lock, flags);
-	return 1;		/* can't take it at the moment */
+	return NETDEV_TX_BUSY;		/* can't take it at the moment */
     }
     spin_unlock_irqrestore(&mp->lock, flags);