genetlink: add and use genl_set_err()

Add a static inline to generic netlink to wrap netlink_set_err()
to make it easier to use here - use it in openvswitch (the only
generic netlink user of netlink_set_err()).

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 8ec8b73..3e2bb15 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -879,8 +879,8 @@
 	if (!IS_ERR(reply))
 		ovs_notify(reply, info, &ovs_dp_flow_multicast_group);
 	else
-		netlink_set_err(sock_net(skb->sk)->genl_sock, 0,
-				ovs_dp_flow_multicast_group.id, PTR_ERR(reply));
+		genl_set_err(sock_net(skb->sk), 0,
+			     ovs_dp_flow_multicast_group.id, PTR_ERR(reply));
 	return 0;
 
 err_flow_free:
@@ -1326,8 +1326,8 @@
 				      info->snd_seq, OVS_DP_CMD_NEW);
 	if (IS_ERR(reply)) {
 		err = PTR_ERR(reply);
-		netlink_set_err(sock_net(skb->sk)->genl_sock, 0,
-				ovs_dp_datapath_multicast_group.id, err);
+		genl_set_err(sock_net(skb->sk), 0,
+			     ovs_dp_datapath_multicast_group.id, err);
 		err = 0;
 		goto unlock;
 	}