tracing/sched: Track per-cpu rt and non-rt cpu_load.

Add a new tracepoint trace_sched_enq_deq_task to track
per-cpu rt and non-rt cpu_load during task enqueue
and dequeue.

This is useful to visualize and compare the load on
different cpus and also to understand how balanced
the load is at any point of time.

Note: We only print cpu_load[0] because we only care about
the most recent load history for tracking load balancer
effectiveness.

Change-Id: I46f0bb84e81652099ed5edf8c2686c70c8b8330c
Signed-off-by: Arun Bharadwaj <abharadw@codeaurora.org>