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/tests/python-use.c

@@ -15,7 +15,7 @@ int test__python_use(int subtest __maybe_unused)
 	int ret;
 
 	if (asprintf(&cmd, "echo \"import sys ; sys.path.append('%s'); import perf\" | %s %s",
-		     PYTHONPATH, PYTHON, verbose ? "" : "2> /dev/null") < 0)
+		     PYTHONPATH, PYTHON, verbose > 0 ? "" : "2> /dev/null") < 0)
 		return -1;
 
 	ret = system(cmd) ? -1 : 0;