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/tokenring/olympic.c b/drivers/net/tokenring/olympic.c
index d068a9d..c369749 100644
--- a/drivers/net/tokenring/olympic.c
+++ b/drivers/net/tokenring/olympic.c
@@ -1055,7 +1055,7 @@
 		return 0;
 	} else {
 		spin_unlock_irqrestore(&olympic_priv->olympic_lock,flags);
-		return 1;
+		return NETDEV_TX_BUSY;
 	} 
 
 }