core_ctl: Manage number of online cores based on system load

The core_ctl module takes input from userspace and CPU load information to
decide how many CPUs to keep online. User space has the following tunables:

- min_cpus: Minimum number of CPUs to keep online. This overrides other
  heuristics.
- max_cpus: Maximum number of CPUs to keep online. This overrides other
  heuristics.
- additional_cpus: Additional idle CPUs to keep ready for use.
- busy_up_thres: The normalized load% threshold that the CPU load should
  exceeded for the CPU to be go from not busy to busy.
  It could be a single threshold for all CPUs in a group, or num_cpus
  thresholds separated by spaces to specify different thresholds based on
  the current number of online CPUs.
- busy_down_thres: The normalized load% threshold that the CPU load should
  be lower than for the CPU to go from busy to not busy.
  It could be a single threshold for all CPUs in a group, or num_cpus
  thresholds separated by spaces to specify different thresholds based on
  the current number of online CPUs.
- offline_delay_ms: The time to wait for before offline cores when the
  number of needed CPUs goes down.

Mot-CRs-fixed: (CR)

Change-Id: Ied1d5bcbb8da5bbd5f3d1a3f042599babace6b65
Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Ravi Chebolu <arc095@motorola.com>
Reviewed-on: http://gerrit.mot.com/866560


SME-Granted: SME Approvals Granted
SLTApproved: Slta Waiver <sltawvr@motorola.com>
Tested-by: Jira Key <jirakey@motorola.com>
Reviewed-by: Lian-Wei Wang <lian-wei.wang@motorola.com>
Reviewed-by: Christopher Fries <cfries@motorola.com>
Submit-Approved: Jira Key <jirakey@motorola.com>