IB/IPoIB: Fix bad error flow in ipoib_add_port()

Error values of ib_query_port() and ib_query_device() weren't propagated
correctly. Because of that, ipoib_add_port() could return NULL value,
which escaped the IS_ERR() check in ipoib_add_one() and we crashed.
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/ulp/ipoib/ipoib_main.c

@@ -1577,7 +1577,8 @@ static struct net_device *ipoib_add_port(const char *format,
 	SET_NETDEV_DEV(priv->dev, hca->dma_device);
 	priv->dev->dev_id = port - 1;
 
-	if (!ib_query_port(hca, port, &attr))
+	result = ib_query_port(hca, port, &attr);
+	if (!result)
 		priv->max_ib_mtu = ib_mtu_enum_to_int(attr.max_mtu);
 	else {
 		printk(KERN_WARNING "%s: ib_query_port %d failed\n",
@@ -1598,7 +1599,8 @@ static struct net_device *ipoib_add_port(const char *format,
 		goto device_init_failed;
 	}
 
-	if (ipoib_set_dev_features(priv, hca))
+	result = ipoib_set_dev_features(priv, hca);
+	if (result)
 		goto device_init_failed;
 
 	/*