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/pmu-events/json.c

@@ -49,7 +49,7 @@ static char *mapfile(const char *fn, size_t *size)
 	int err;
 	int fd = open(fn, O_RDONLY);
 
-	if (fd < 0 && verbose && fn) {
+	if (fd < 0 && verbose > 0 && fn) {
 		pr_err("Error opening events file '%s': %s\n", fn,
 				strerror(errno));
 	}