sched: walt: improve the scheduler

This change is for general scheduler improvements.

Change-Id: I567213580a970abc374d95e3d1fdc0aa73eaf705
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>
Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>
[satyap@codeaurora.org: resolve trivial merge conflicts]
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>