netconf: advertise mc_forwarding status

This patch advertise the MC_FORWARDING status for IPv4 and IPv6.
This field is readonly, only multicast engine in the kernel updates it.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/uapi/linux/netconf.h b/include/uapi/linux/netconf.h
index 75dcbc5..64804a7 100644
--- a/include/uapi/linux/netconf.h
+++ b/include/uapi/linux/netconf.h
@@ -13,6 +13,7 @@
 	NETCONFA_IFINDEX,
 	NETCONFA_FORWARDING,
 	NETCONFA_RP_FILTER,
+	NETCONFA_MC_FORWARDING,
 	__NETCONFA_MAX
 };
 #define NETCONFA_MAX	(__NETCONFA_MAX - 1)