src: use NFPROTO_ constants

Resync netfilter.h from the latest kernel and make use of the new
NFPROTO_ constants that have been introduced.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/ip6tables.c b/ip6tables.c
index 989f3bc..293ba37 100644
--- a/ip6tables.c
+++ b/ip6tables.c
@@ -199,7 +199,7 @@
 };
 
 struct afinfo afinfo = {
-	.family		= AF_INET6,
+	.family		= NFPROTO_IPV6,
 	.libprefix	= "libip6t_",
 	.ipproto	= IPPROTO_IPV6,
 	.kmod		= "ip6_tables",