cgroup: relocate cgroup_rm_cftypes()

cftype handling is about to be revamped.  Relocate cgroup_rm_cftypes()
above cgroup_add_cftypes() in preparation.  This is pure relocation.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>