trace/sched: Fix compilation issues on !SMP

Compilation fails on !SMP systems due to scheduler trace points.
Fix the issue by making them available only on SMP system.

Change-Id: Idedf12b6b0bb486184f06a8e9972bae677d9bc97
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>