sched: Introduce a different version of freq aggregation

This version sets up a timer every tick when RESTRAINED boost is turned
on. In the timer handler, we take all rq locks and aggregate the group
load for all clusters. This aggregate load is then reported while
restrained boost remains on. This is not perfect since it ignores the
changes in group load due to inter cluster migrations for one tick.
But this is the best we can do.

Change-Id: Iaa7aa64c8fd651a9f0b084f091d25aa4241b37dd
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>