netfilter: xtables: switch table AFs to nfproto

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
diff --git a/net/ipv4/netfilter/nf_nat_rule.c b/net/ipv4/netfilter/nf_nat_rule.c
index 6348a79..6448a9b 100644
--- a/net/ipv4/netfilter/nf_nat_rule.c
+++ b/net/ipv4/netfilter/nf_nat_rule.c
@@ -62,7 +62,7 @@
 	.name		= "nat",
 	.valid_hooks	= NAT_VALID_HOOKS,
 	.me		= THIS_MODULE,
-	.af		= AF_INET,
+	.af		= NFPROTO_IPV4,
 };
 
 /* Source NAT */