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/depca.c b/drivers/net/depca.c
index 9301eb2..97ea2d6 100644
--- a/drivers/net/depca.c
+++ b/drivers/net/depca.c
@@ -957,7 +957,7 @@
 		if (TX_BUFFS_AVAIL)
 			netif_start_queue(dev);
 	} else
-		status = -1;
+		status = NETDEV_TX_LOCKED;
 
       out:
 	return status;
@@ -1839,7 +1839,7 @@
 
 		lp->tx_new = (++end) & lp->txRingMask;	/* update current pointers */
 	} else {
-		status = -1;
+		status = NETDEV_TX_LOCKED;
 	}
 
 	return status;