sched/trace: Add sched_task_util trace point

Add sched_task_util trace point for debugging issues
related to why scheduler chosen a specific CPU for
placing task.

Change-Id: I48c91651f7cbd3eaf0640f38380bb51aa693b16f
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>