sched/fair: Improve the scheduler

This change is for general scheduler improvement.

Change-Id: I15c01c20691899053e0aa760923ba0db644f2b73
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
[satyap@codeaurora.org: port to 5.4 and resolve trivial merge conflicts]
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>