netns: move {inc,dec}_net_namespaces into #ifdef

With the newly enforced limit on the number of namespaces,
we get a build warning if CONFIG_NETNS is disabled:

net/core/net_namespace.c:273:13: error: 'dec_net_namespaces' defined but not used [-Werror=unused-function]
net/core/net_namespace.c:268:24: error: 'inc_net_namespaces' defined but not used [-Werror=unused-function]

This moves the two added functions inside the #ifdef that guards
their callers.

Fixes: 703286608a22 ("netns: Add a limit on the number of net namespaces")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

net/core/net_namespace.c

@@ -266,16 +266,6 @@ struct net *get_net_ns_by_id(struct net *net, int id)
 	return peer;
 }
 
-static struct ucounts *inc_net_namespaces(struct user_namespace *ns)
-{
-	return inc_ucount(ns, current_euid(), UCOUNT_NET_NAMESPACES);
-}
-
-static void dec_net_namespaces(struct ucounts *ucounts)
-{
-	dec_ucount(ucounts, UCOUNT_NET_NAMESPACES);
-}
-
 /*
  * setup_net runs the initializers for the network namespace object.
  */
@@ -320,6 +310,16 @@ out_undo:
 
 
 #ifdef CONFIG_NET_NS
+static struct ucounts *inc_net_namespaces(struct user_namespace *ns)
+{
+	return inc_ucount(ns, current_euid(), UCOUNT_NET_NAMESPACES);
+}
+
+static void dec_net_namespaces(struct ucounts *ucounts)
+{
+	dec_ucount(ucounts, UCOUNT_NET_NAMESPACES);
+}
+
 static struct kmem_cache *net_cachep;
 static struct workqueue_struct *netns_wq;