sched/walt: Improve the scheduler

This change is for general scheduler improvement.

Change-Id: I4d860d155697178feaed9c6418bf9fa1f773180c
Signed-off-by: Kishore Sri venkata Ganesh Bolisetty <bsrivenk@codeaurora.org>
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>