sched: Avoid pulling big tasks to the little cluster during load balance

When a lower capacity CPU attempts to pull work from a higher capacity CPU,
during load balance, it does not distinguish between tasks that will fit
or not fit on the destination CPU. This causes suboptimal load balancing
decisions whereby big tasks end up on the lower capacity CPUs and little
tasks remain on higher capacity CPUs. Avoid this behavior, by first
restricting search to only include tasks that fit on the destination CPU.
If such a task cannot be found, remove this restriction so that any task
can be pulled over to the destination CPU. This behavior is not applicable
during sched_boost, however, as none of the tasks will fit on a lower
capacity CPU.

Change-Id: I1093420a629a0886fc3375849372ab7cf42e928e
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>