perf test: Fixup error reporting in basic mmap test

In two cases this test could detect an error, bail out but return zero.
Fix it by reporting -1 for failure.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-tjhs9v6nqpofmxv3gs5lnu2c@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/mmap-basic.c

@@ -128,6 +128,7 @@ int test__basic_mmap(void)
 			goto out_munmap;
 		}
 
+		err = -1;
 		evsel = perf_evlist__id2evsel(evlist, sample.id);
 		if (evsel == NULL) {
 			pr_debug("event with id %" PRIu64
@@ -137,16 +138,17 @@ int test__basic_mmap(void)
 		nr_events[evsel->idx]++;
 	}
 
+	err = 0;
 	list_for_each_entry(evsel, &evlist->entries, node) {
 		if (nr_events[evsel->idx] != expected_nr_events[evsel->idx]) {
 			pr_debug("expected %d %s events, got %d\n",
 				 expected_nr_events[evsel->idx],
 				 perf_evsel__name(evsel), nr_events[evsel->idx]);
+			err = -1;
 			goto out_munmap;
 		}
 	}
 
-	err = 0;
 out_munmap:
 	perf_evlist__munmap(evlist);
 out_close_fd: