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/hamachi.c b/drivers/net/hamachi.c
index 26151fa..9d5b62c 100644
--- a/drivers/net/hamachi.c
+++ b/drivers/net/hamachi.c
@@ -1280,7 +1280,7 @@
 		status=readw(hmp->base + TxStatus);
 		if( !(status & 0x0001) || (status & 0x0002))
 			writew(0x0001, hmp->base + TxCmd);
-		return 1;
+		return NETDEV_TX_BUSY;
 	}
 
 	/* Caution: the write order is important here, set the field