vxlan: source compatiablity with IFLA_VXLAN_GROUP (v2)

Source compatiability for build iproute2 was broken by:
  commit c7995c43facc6e5dea4de63fa9d283a337aabeb1
  Author: Atzm Watanabe <atzm@stratosphere.co.jp>
    vxlan: Allow setting destination to unicast address.

Since this commit has not made it upstream (still net-next),
and better to avoid gratitious changes to exported API's;
go back to original definition, and add a comment.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index e316354..5346131 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -297,7 +297,7 @@
 enum {
 	IFLA_VXLAN_UNSPEC,
 	IFLA_VXLAN_ID,
-	IFLA_VXLAN_REMOTE,
+	IFLA_VXLAN_GROUP,	/* group or remote address */
 	IFLA_VXLAN_LINK,
 	IFLA_VXLAN_LOCAL,
 	IFLA_VXLAN_TTL,