sched/events: Introduce overutilized trace event

Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Signed-off-by: Andres Oportus <andresoportus@google.com>
(cherry picked from commit 8e45d941282039d5379f4e286e5bd0a2044e105c)
[ - Trivial cherry pick issues
  - Changed commit title for consistency ]
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
Change-Id: I78fb5e82223558def0cf16105c233591cda81d5c
(cherry picked from commit 3f88c4dda88350af7e8aef56a602752168190fc9)
[ - Trivial cherry pick issues
  - Whitespace cleanup ]
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>