netfilter: nf_tables: get rid of the expression example code

There's an example net/netfilter/nft_expr_template.c example file in tree that
got out of sync along time, remove it.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: Patrick McHardy <kaber@trash.net>

net/netfilter/nft_expr_template.c

-/*
- * Copyright (c) 2008-2009 Patrick McHardy <kaber@trash.net>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- *
- * Development of this code funded by Astaro AG (http://www.astaro.com/)
- */
-
-#include <linux/kernel.h>
-#include <linux/init.h>
-#include <linux/netlink.h>
-#include <linux/netfilter.h>
-#include <linux/netfilter/nf_tables.h>
-#include <net/netfilter/nf_tables.h>
-
-struct nft_template {
-
-};
-
-static void nft_template_eval(const struct nft_expr *expr,
-			      struct nft_data data[NFT_REG_MAX + 1],
-			      const struct nft_pktinfo *pkt)
-{
-	struct nft_template *priv = nft_expr_priv(expr);
-
-}
-
-static const struct nla_policy nft_template_policy[NFTA_TEMPLATE_MAX + 1] = {
-	[NFTA_TEMPLATE_ATTR]		= { .type = NLA_U32 },
-};
-
-static int nft_template_init(const struct nft_ctx *ctx,
-			   const struct nft_expr *expr,
-			   const struct nlattr * const tb[])
-{
-	struct nft_template *priv = nft_expr_priv(expr);
-
-	return 0;
-}
-
-static void nft_template_destroy(const struct nft_ctx *ctx,
-			       const struct nft_expr *expr)
-{
-	struct nft_template *priv = nft_expr_priv(expr);
-
-}
-
-static int nft_template_dump(struct sk_buff *skb, const struct nft_expr *expr)
-{
-	const struct nft_template *priv = nft_expr_priv(expr);
-
-	NLA_PUT_BE32(skb, NFTA_TEMPLATE_ATTR, priv->field);
-	return 0;
-
-nla_put_failure:
-	return -1;
-}
-
-static struct nft_expr_type nft_template_type;
-static const struct nft_expr_ops nft_template_ops = {
-	.type		= &nft_template_type,
-	.size		= NFT_EXPR_SIZE(sizeof(struct nft_template)),
-	.eval		= nft_template_eval,
-	.init		= nft_template_init,
-	.destroy	= nft_template_destroy,
-	.dump		= nft_template_dump,
-};
-
-static struct nft_expr_type nft_template_type __read_mostly = {
-	.name		= "template",
-	.ops		= &nft_template_ops,
-	.policy		= nft_template_policy,
-	.maxattr	= NFTA_TEMPLATE_MAX,
-	.owner		= THIS_MODULE,
-};
-
-static int __init nft_template_module_init(void)
-{
-	return nft_register_expr(&nft_template_type);
-}
-
-static void __exit nft_template_module_exit(void)
-{
-	nft_unregister_expr(&nft_template_type);
-}
-
-module_init(nft_template_module_init);
-module_exit(nft_template_module_exit);
-
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
-MODULE_ALIAS_NFT_EXPR("template");