cgroup:namespace: Remove unused cgroup_namespaces_init()

cgroup_namspace_init() just return 0. Therefore, there is no need to
call it during start_kernel. Just remove it.

Fixes: a79a908f ("cgroup: introduce cgroup namespaces")
Signed-off-by: Lu Jialin <lujialin4@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/cgroup/namespace.c

@@ -149,9 +149,3 @@ const struct proc_ns_operations cgroupns_operations = {
 	.install	= cgroupns_install,
 	.owner		= cgroupns_owner,
 };
-
-static __init int cgroup_namespaces_init(void)
-{
-	return 0;
-}
-subsys_initcall(cgroup_namespaces_init);