sched/fair: Sync task util before EAS wakeup

sched/fair: Sync task util before EAS wakeup

Before using a task's util_avg signal in EAS, we need to ensure that
it has been synced up to the last_update_time of prev_cpu's root
cfs_rq.

We previously relied on the side effect of wake_cap to do that,
however that does not happen when the waking CPU has the same
capacity as the prev_cpu. Therefore just explicitly call
sync_entity_load_avg. This may result in calling that function twice
within the same select_task_rq_fair, but since last_update_time
hasn't changed the second call will bail out very quickly.

Change-Id: I91f1fcd71dfeb96b7f5b73418f1cf9ac311d4655
Signed-off-by: Brendan Jackman <brendan.jackman@arm.com>
Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>