Revert "cgroup: Avoid -Wstringop-overflow warnings"

This reverts commit 36de5f3.

The commit caused boot failures on some configurations due to cgroup
hierarchies not being created at all.

Signed-off-by: Tejun Heo <tj@kernel.org>

Author: htejun

kernel/cgroup/cgroup.c

@@ -1198,9 +1198,6 @@ static struct css_set *find_css_set(struct css_set *old_cset,
 	unsigned long key;
 	int ssid;
 
-	if (!CGROUP_HAS_SUBSYS_CONFIG)
-		return NULL;
-
 	lockdep_assert_held(&cgroup_mutex);
 
 	/* First see if we already have a cgroup group that matches
@@ -6020,9 +6017,6 @@ int __init cgroup_init(void)
 	struct cgroup_subsys *ss;
 	int ssid;
 
-	if (!CGROUP_HAS_SUBSYS_CONFIG)
-		return -EINVAL;
-
 	BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16);
 	BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
 	BUG_ON(cgroup_init_cftypes(NULL, cgroup_psi_files));