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/libipt_MIRROR.c b/extensions/libipt_MIRROR.c
index 0365f47..1322f59 100644
--- a/extensions/libipt_MIRROR.c
+++ b/extensions/libipt_MIRROR.c
@@ -21,7 +21,7 @@
 static struct xtables_target mirror_tg_reg = {
 	.name		= "MIRROR",
 	.version	= XTABLES_VERSION,
-	.family		= PF_INET,
+	.family		= NFPROTO_IPV4,
 	.size		= XT_ALIGN(0),
 	.userspacesize	= XT_ALIGN(0),
  	.help		= MIRROR_help,