netfilter: nf_tables: merge exthdr expression into nft core

before:
   text    data     bss     dec     hex filename
   5056     844       0    5900    170c net/netfilter/nft_exthdr.ko
 102456    2316     401  105173   19ad5 net/netfilter/nf_tables.ko

after:
 106410    2392     401  109203   1aa93 net/netfilter/nf_tables.ko

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
index 47ec104..a940c9f 100644
--- a/net/netfilter/nft_exthdr.c
+++ b/net/netfilter/nft_exthdr.c
@@ -10,11 +10,10 @@
 
 #include <asm/unaligned.h>
 #include <linux/kernel.h>
-#include <linux/init.h>
-#include <linux/module.h>
 #include <linux/netlink.h>
 #include <linux/netfilter.h>
 #include <linux/netfilter/nf_tables.h>
+#include <net/netfilter/nf_tables_core.h>
 #include <net/netfilter/nf_tables.h>
 #include <net/tcp.h>
 
@@ -353,7 +352,6 @@ static int nft_exthdr_dump_set(struct sk_buff *skb, const struct nft_expr *expr)
 	return nft_exthdr_dump_common(skb, priv);
 }
 
-static struct nft_expr_type nft_exthdr_type;
 static const struct nft_expr_ops nft_exthdr_ipv6_ops = {
 	.type		= &nft_exthdr_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_exthdr)),
@@ -407,27 +405,10 @@ nft_exthdr_select_ops(const struct nft_ctx *ctx,
 	return ERR_PTR(-EOPNOTSUPP);
 }
 
-static struct nft_expr_type nft_exthdr_type __read_mostly = {
+struct nft_expr_type nft_exthdr_type __read_mostly = {
 	.name		= "exthdr",
 	.select_ops	= nft_exthdr_select_ops,
 	.policy		= nft_exthdr_policy,
 	.maxattr	= NFTA_EXTHDR_MAX,
 	.owner		= THIS_MODULE,
 };
-
-static int __init nft_exthdr_module_init(void)
-{
-	return nft_register_expr(&nft_exthdr_type);
-}
-
-static void __exit nft_exthdr_module_exit(void)
-{
-	nft_unregister_expr(&nft_exthdr_type);
-}
-
-module_init(nft_exthdr_module_init);
-module_exit(nft_exthdr_module_exit);
-
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
-MODULE_ALIAS_NFT_EXPR("exthdr");