cgroup_migrate() has the destination cgroup as the first parameter
while cgroup_task_migrate() has the destination cset as the last.
Another migration function is scheduled to be added which can make the
discrepancy further stand out.  Let's reorder cgroup_migrate()'s
parameters so that the destination cgroup is the last.

This doesn't cause any functional difference.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NZefan Li <lizefan@huawei.com>