selftests: cgroup: Make cg_create() use 0755 for permission instead of 0644

0644 is an odd perm to create a cgroup which is a directory. Use the regular
0755 instead. This is necessary for euid switching test case.
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

tools/testing/selftests/cgroup/cgroup_util.c

@@ -221,7 +221,7 @@ int cg_find_unified_root(char *root, size_t len)
 
 int cg_create(const char *cgroup)
 {
-	return mkdir(cgroup, 0644);
+	return mkdir(cgroup, 0755);
 }
 
 int cg_wait_for_proc_count(const char *cgroup, int count)