cgroup: make flags and subsys_masks unsigned int

There's no reason to use atomic bitops for cgroup_subsys_state->flags,
cgroup_root->flags and various subsys_masks.  This patch updates those
to use bitwise and/or operations instead and converts them form
unsigned long to unsigned int.

This makes the fields occupy (marginally) smaller space and makes it
clear that they don't require atomicity.

This patch doesn't cause any behavior difference.

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