tracing/sched: Clean up preemptoff/irqsoff extensions

preemptoff/irqsoff tracers are extended to print call stack,
when preemption/irqs are disabled more than a threshold. The
subsequent patches brings the same functionality in a GKI
friendly manner. So, clean up the existing code that does this.

Change-Id: Id86c298d3a044f7c7e99170ea74f79adbe6786a4
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>