qeth: meaningful return code for set_mac_address

Setting an invalid mac-address for a qeth layer2 device returns
with a strange error code:
# ip link set hsi1 address 00:00:00:00:00:01
   RTNETLINK answers: Unknown error 18446744073709486085
Problem is caused by wrong usage of the return_code field within
structure qeth_ipa_cmd.
With this patch the ip command above returns
   SIOCSIFHWADDR: Invalid argument

Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/s390/net/qeth_l2_main.c b/drivers/s390/net/qeth_l2_main.c
index e5c9cf1..0e7c29d 100644
--- a/drivers/s390/net/qeth_l2_main.c
+++ b/drivers/s390/net/qeth_l2_main.c
@@ -576,7 +576,6 @@
 		default:
 			break;
 		}
-		cmd->hdr.return_code = -EIO;
 	} else {
 		card->info.mac_bits |= QETH_LAYER2_MAC_REGISTERED;
 		memcpy(card->dev->dev_addr, cmd->data.setdelmac.mac,
@@ -605,7 +604,6 @@
 	cmd = (struct qeth_ipa_cmd *) data;
 	if (cmd->hdr.return_code) {
 		QETH_CARD_TEXT_(card, 2, "err%d", cmd->hdr.return_code);
-		cmd->hdr.return_code = -EIO;
 		return 0;
 	}
 	card->info.mac_bits &= ~QETH_LAYER2_MAC_REGISTERED;
@@ -682,7 +680,7 @@
 	rc = qeth_l2_send_delmac(card, &card->dev->dev_addr[0]);
 	if (!rc)
 		rc = qeth_l2_send_setmac(card, addr->sa_data);
-	return rc;
+	return rc ? -EINVAL : 0;
 }
 
 static void qeth_l2_set_multicast_list(struct net_device *dev)