sched/fair: Improve the scheduler

This change is for general scheduler improvement.

Change-Id: I7e6cc760a6add9ebdab7d67a176559bc640f7790
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>
[satyap@codeaurora.org: port to 5.4 and minor update for WALT]
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>