Revert "sched/fair: Don't let tasks slip away from gold to silver cluster"

If we ever wanted to stop big tasks from being balanced out to smaller cluster,
it had already been done by checking the tasks in can_migrate_task() with
schedtune

This commit, however, introduces a bug that light tasks including non-big tasks
not being balanced out to smaller cluster, resulting in big cluster being
occasionally overloaded

This reverts commit d89e0499.

Change-Id: I72bbd526c8b4e0aabb7533cbdb5141593016dbb5
Signed-off-by: Diep Quynh <remilia.1505@gmail.com>
Signed-off-by: Alexander Winkowski <dereference23@outlook.com>