perf tests: Factor out print_hists_*()

Those print helper functions can be reused by later hist test cases so
factor them out to a common location.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1400480762-22852-20-git-send-email-namhyung@kernel.org


Signed-off-by: Jiri Olsa <jolsa@kernel.org>