trace_stat: keep original order

Impact: make trace_stat files show items with the original order

trace_stat tracer reverse the items, it makes the output
looks a little ugly.

Example, when we read trace_stat/workqueues, we get cpu#7's stat.
at first, and then cpu#6... cpu#0.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <49C9F23F.5040307@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>