perf test: Keep test result clean if '-v' not set

According to [1], 'perf test' should avoid output too much information
if '-v' is not set, only 'Ok', 'FAIL' or 'Skip' need to be printed.

This patch removes several messages sent directly to stderr to make
the output clean.

Before this patch:

  # perf test dummy
  23: Test using a dummy software event to keep tracking       : (not supported) Ok

After this patch:

  # perf test dummy
  23: Test using a dummy software event to keep tracking       : Skip

[1] http://lkml.kernel.org/r/20151020134155.GE4400@redhat.com

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1446547486-229499-2-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/tests/switch-tracking.c b/tools/perf/tests/switch-tracking.c
index e698742..a02af50 100644
--- a/tools/perf/tests/switch-tracking.c
+++ b/tools/perf/tests/switch-tracking.c
@@ -366,7 +366,7 @@
 
 	/* Third event */
 	if (!perf_evlist__can_select_event(evlist, sched_switch)) {
-		fprintf(stderr, " (no sched_switch)");
+		pr_debug("No sched_switch\n");
 		err = 0;
 		goto out;
 	}
@@ -442,7 +442,7 @@
 	}
 
 	if (perf_evlist__open(evlist) < 0) {
-		fprintf(stderr, " (not supported)");
+		pr_debug("Not supported\n");
 		err = 0;
 		goto out;
 	}