sched: update placement logic to prefer C-state and busier CPUs

Update the wakeup placement logic when need_idle is not set. Break
ties in power with C-state. If C-state is the same break ties with
prev_cpu. Finally go for the most loaded CPU.

CRs-fixed: 1006303
Change-Id: Iafa98a909ed464af33f4fe3345bbfc8e77dee963
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>
[joonwoop@codeaurora.org: fixed bug where assigns best_cpu_cstate with
 uninitialized cpu_cstate.]
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>