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/lib8390.c b/drivers/net/lib8390.c
index 789b6cb..f28c233 100644
--- a/drivers/net/lib8390.c
+++ b/drivers/net/lib8390.c
@@ -370,7 +370,7 @@
 		spin_unlock(&ei_local->page_lock);
 		enable_irq_lockdep_irqrestore(dev->irq, &flags);
 		dev->stats.tx_errors++;
-		return 1;
+		return NETDEV_TX_BUSY;
 	}
 
 	/*