sched: walt: select sysctl_sched_is_big_little dynamically

If the energy model indicates that there is an overlap between
the clusters, set sysctl_sched_is_big_little to 0.

Change-Id: Iaf633a69809f325120e7a77ae0747f42deb6ae7f
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>