sched/walt: Improve the scheduler

This change is for general scheduler improvements.

Change-Id: I5f19453ec1a19c71d67a02c3f0ec9967e7673a4b
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
[satyap@codeaurora.org: fix trivial merge conflicts]
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>