sched: EAS/WALT: finish accounting prior to task_tick

In order to set rq->misfit_task in time, call update_task_ravg() prior
to task_tick.  This reduces upmigration delay by 1 scheduler window.

Change-Id: I7cc80badd423f2e7684125fbfd853b0a3610f0e8
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>
(cherry picked from commit ed9e74966829b60ca2a2cd39cdcb0824a87a4da2)
[Trivial cherry-pick issue]
Signed-off-by: Quentin Perret <quentin.perret@arm.com>