cgroup/cpuset: Account for boot time isolated CPUs

cgroup/cpuset: Account for boot time isolated CPUs

With the "isolcpus" boot command line parameter, we are able to
create isolated CPUs at boot time. These isolated CPUs aren't fully
accounted for in the cpuset code. For instance, the root cgroup's
"cpuset.cpus.isolated" control file does not include the boot time
isolated CPUs. Fix that by looking for pre-isolated CPUs at init time.

The prstate_housekeeping_conflict() function does check the
HK_TYPE_DOMAIN housekeeping cpumask to make sure that CPUs outside of it
can only be used in isolated partition. Given the fact that we are going
to make housekeeping cpumasks dynamic, the current check may not be right
anymore. Save the boot time HK_TYPE_DOMAIN cpumask and check against
it instead of the upcoming dynamic HK_TYPE_DOMAIN housekeeping cpumask.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>