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/code-reading.c

@@ -599,7 +599,7 @@ static int do_test_code_reading(bool try_kcore)
 				continue;
 			}
 
-			if (verbose) {
+			if (verbose > 0) {
 				char errbuf[512];
 				perf_evlist__strerror_open(evlist, errno, errbuf, sizeof(errbuf));
 				pr_debug("perf_evlist__open() failed!\n%s\n", errbuf);