batman-adv: Return error codes instead of -1 on failures

Signed-off-by: Sven Eckelmann <sven@narfation.org>
diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index dc334fa..ce78c6d 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -306,10 +306,8 @@
 	bat_priv = netdev_priv(hard_iface->soft_iface);
 
 	ret = bat_priv->bat_algo_ops->bat_iface_enable(hard_iface);
-	if (ret < 0) {
-		ret = -ENOMEM;
+	if (ret < 0)
 		goto err_dev;
-	}
 
 	hard_iface->if_num = bat_priv->num_ifaces;
 	bat_priv->num_ifaces++;