sched: avoid CPUs with high irq activity for non-small tasks

The irq-aware scheduler is to achieve better performance by avoiding task
placement to the CPUs which have high irq activity.  However current
scheduler places tasks to the CPUs which are loaded by irq activity
preferably as opposed to what it is meant to be when the task is non-small.
This is suboptimal for both power and performance.
Fix task placement algorithm to avoid CPUs with significant irq activities.

Change-Id: Ifa5a6ac186241bd58fa614e93e3d873a5f5ad4ca
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>