trace: filter out spurious preemption and IRQs disable traces

Spurious preemption and IRQs disable traces are observed when
CPUs coming out of LPMs or while switching from idle task to
other task. Add necessary checks to filter out spurious traces.

Change-Id: I82bfde23e7a0837098d96a77c84be9981207571a
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>