cgroup: Do not report unavailable v1 controllers in /proc/cgroups

This is a followup to CONFIG-urability of cpuset and memory controllers
for v1 hierarchies. Make the output in /proc/cgroups reflect that
!CONFIG_CPUSETS_V1 is like !CONFIG_CPUSETS and
!CONFIG_MEMCG_V1 is like !CONFIG_MEMCG.

The intended effect is that hiding the unavailable controllers will hint
users not to try mounting them on v1.

Signed-off-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>