core_ctl: un-isolate BIG CPUs more aggressively

The current algorithm to bring additional BIG CPUs is very
conservative. It works when BIG tasks alone run on BIG
cluster. When co-location and scheduler boost features
are activated, small/medium tasks also run on BIG cluster.
We don't want these tasks to downmigrate, when BIG CPUs are
available but isolated. The following changes are done to
un-isolate CPUs more aggressively.

(1) Round up the big_avg. When the big_avg indicates that
there are 1.5 tasks on an average in the last window, it
indicates that we need 2 BIG CPUs not 1 BIG CPU.

(2) Track the maximum number of running tasks in the last
window on all CPUs. If any of the CPU in a cluster has more
than 4 runnable tasks in the last window, bring an additional
CPU to help out.

Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
[markivx: Retain core_ctl changes alone]
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>

Change-Id: I39ca6aa52cb7e0d3798d4c69f4285e3ed9a8bac9
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>