cgroup: relocate cgroup_populate_dir()
cgroup: relocate cgroup_populate_dir()

Move it upwards so that it's right below cgroup_clear_dir() and the
forward declaration is unnecessary.

Signed-off-by: Tejun Heo <546b05909706652891a87f7bfe385ae147f61f91@kernel.org>
Cc: Li Zefan <a8167b9d27aca9c6624754deb52c4c6420eded04@huawei.com>
Cc: Johannes Weiner <331be22c6b63ca3e0a03d408c2d906b1b02cd5f2@cmpxchg.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs