sched: let sched_boost take precedence over sched_restrict_cluster_spill

When sched_restrict_cluster_spill knob is enabled, RT tasks are restricted
to lower power cluster. This knob also restricts inter cluster no-hz kicks.
Ignore this knob setting when sched_boost is enabled so that tasks are
placed on CPUs with highest spare capacity.

CRs-Fixed: 968852
Change-Id: I01b3fc10b39dc834a733d64c2ee29c308d7ff730
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>