netfilter: netns nf_conntrack: per-netns net.netfilter.nf_conntrack_count sysctl

Note, sysctl table is always duplicated, this is simpler and less
special-cased.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/include/net/netns/conntrack.h b/include/net/netns/conntrack.h
index fc0a46d..2b50758 100644
--- a/include/net/netns/conntrack.h
+++ b/include/net/netns/conntrack.h
@@ -4,6 +4,7 @@
 #include <linux/list.h>
 #include <asm/atomic.h>
 
+struct ctl_table_header;
 struct nf_conntrack_ecache;
 
 struct netns_ct {
@@ -16,6 +17,9 @@
 #ifdef CONFIG_NF_CONNTRACK_EVENTS
 	struct nf_conntrack_ecache *ecache;
 #endif
+#ifdef CONFIG_SYSCTL
+	struct ctl_table_header	*sysctl_header;
+#endif
 	int			hash_vmalloc;
 	int			expect_vmalloc;
 };