trace/sched: fix compilation issue for UP systems

sched_enq_deq_task trace point calls cpu_util which is
only available for SMP systems and leads to compilation
issue on UP systems. Also, cpu_util only accounts for
CFS tasks.

Change-Id: I8b15d1c2bcba6de65397bbeb0b6772fefcc464a2
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>