DEBUG: sched/fair: Fix missing sched_load_avg_cpu events

update_cfs_rq_load_avg is called from update_blocked_averages without triggering
the sched_load_avg_cpu event. Move the event trigger to inside
update_cfs_rq_load_avg to avoid this missing event.

Change-Id: I9f72e297a0687bfeba0d41bd002623fbf3c601ee
Signed-off-by: Brendan Jackman <brendan.jackman@arm.com>