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/extensions/libip6t_rt.c b/extensions/libip6t_rt.c
index 207f515..25e410c 100644
--- a/extensions/libip6t_rt.c
+++ b/extensions/libip6t_rt.c
@@ -326,7 +326,7 @@
 static struct xtables_match rt_mt6_reg = {
 	.name		= "rt",
 	.version	= XTABLES_VERSION,
-	.family		= PF_INET6,
+	.family		= NFPROTO_IPV6,
 	.size		= XT_ALIGN(sizeof(struct ip6t_rt)),
 	.userspacesize	= XT_ALIGN(sizeof(struct ip6t_rt)),
 	.help		= rt_help,