net, netns_xt: shrink netns_xt members

In case if kernel was compiled without ebtables support
there is no need to keep ebt_table pointers in netns_xt
structure.

Make it config dependent.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/netns/x_tables.h

@@ -8,8 +8,11 @@ struct ebt_table;
 
 struct netns_xt {
 	struct list_head tables[NFPROTO_NUMPROTO];
+#if defined(CONFIG_BRIDGE_NF_EBTABLES) || \
+    defined(CONFIG_BRIDGE_NF_EBTABLES_MODULE)
 	struct ebt_table *broute_table;
 	struct ebt_table *frame_filter;
 	struct ebt_table *frame_nat;
+#endif
 };
 #endif