core_ctl: Isolate not_preferred CPUs first during max_cpus limiting

When CPUs are limited via max_cpus tunable, core_ctl first try
to isolate the non busy CPUs. During this, not_preferred CPUs are
skipped. If more CPUs have to be isolated, CPUs are isolated
in the sequential order without checking not_preferred hint.
So we may end up keeping not_preferred CPUs active after this
step. Add another step to isolate the not_preferred CPUs first
during max_cpus limiting.

Change-Id: If2c5c9d9c69718c1e586cd81c1af0ed0b5d13075
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>