perf utils: Check verbose flag properly

It now can have negative value to suppress the message entirely.  So it
needs to check it being positive.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: kernel-team@lge.com
Link: http://lkml.kernel.org/r/20170217081742.17417-3-namhyung@kernel.org
[ Adjust fuzz on tools/perf/util/pmu.c, add > 0 checks in many other places ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-diff.c

@@ -744,7 +744,7 @@ static void data_process(void)
 
 		first = false;
 
-		if (verbose || data__files_cnt > 2)
+		if (verbose > 0 || data__files_cnt > 2)
 			data__fprintf();
 
 		/* Don't sort callchain for perf diff */