sched/walt: Improve the scheduler

This change is for general scheduler improvement.

Change-Id: Id1692f724f2efd22ada3365cebd154f1999930b5
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
[clingutla@codeaurora.org: Resolved trivial merge conflicts]
Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>