tracing: report_latency() in trace_irqsoff.c can return boolean

This patch makes report_latency return bool due to this
particular function only using either one or zero as its
return value.

No functional change.

Link: http://lkml.kernel.org/r/1443537816-5788-3-git-send-email-bywxiaobai@163.com



Signed-off-by: Yaowei Bai <bywxiaobai@163.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>