cpuset: Remove cpuset_update_active_cpus()'s parameter.

In cpuset_update_active_cpus(), cpu_online isn't used anymore. Remove
it.

Signed-off-by: Rakib <Mullick&lt;rakib.mullick@gmail.com>
Acked-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>