[NETLINK]: Put {IFA,IFLA}_{RTA,PAYLOAD} macros back for userspace.

GLIBC uses them etc.

They are guarded by ifndef __KERNEL__ so nobody will start
accidently using them in the kernel again, it's just for
userspace.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/if_link.h b/include/linux/if_link.h
index e963a07..35ed3b5 100644
--- a/include/linux/if_link.h
+++ b/include/linux/if_link.h
@@ -82,6 +82,12 @@
 
 #define IFLA_MAX (__IFLA_MAX - 1)
 
+/* backwards compatibility for userspace */
+#ifndef __KERNEL__
+#define IFLA_RTA(r)  ((struct rtattr*)(((char*)(r)) + NLMSG_ALIGN(sizeof(struct ifinfomsg))))
+#define IFLA_PAYLOAD(n) NLMSG_PAYLOAD(n,sizeof(struct ifinfomsg))
+#endif
+
 /* ifi_flags.
 
    IFF_* flags.