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/8139cp.c b/drivers/net/8139cp.c
index c9fc0ff..50efde1 100644
--- a/drivers/net/8139cp.c
+++ b/drivers/net/8139cp.c
@@ -756,7 +756,7 @@
 		spin_unlock_irqrestore(&cp->lock, intr_flags);
 		pr_err(PFX "%s: BUG! Tx Ring full when queue awake!\n",
 		       dev->name);
-		return 1;
+		return NETDEV_TX_BUSY;
 	}
 
 #if CP_VLAN_TAG_USED