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/sis900.c b/drivers/net/sis900.c
index 2d4617b..a9a897b 100644
--- a/drivers/net/sis900.c
+++ b/drivers/net/sis900.c
@@ -1584,7 +1584,7 @@
 	/* Don't transmit data before the complete of auto-negotiation */
 	if(!sis_priv->autong_complete){
 		netif_stop_queue(net_dev);
-		return 1;
+		return NETDEV_TX_BUSY;
 	}
 
 	spin_lock_irqsave(&sis_priv->lock, flags);