perf probe: Return errno when not hitting any event

On old perf, when using 'perf probe -d' to delete an inexistent event,
it returns errno, eg,

  -bash-4.3# perf probe -d xxx  || echo $?
  Info: Event "*:xxx" does not exist.
    Error: Failed to delete events.
  255

But now perf_del_probe_events() will always set ret = 0, different from
previous del_perf_probe_events(). After this, it returns errno again,
eg,

  -bash-4.3# ./perf probe -d xxx  || echo $?
  "xxx" does not hit any event.
    Error: Failed to delete events.
  254

And it is more appropriate to return -ENOENT instead of -EPERM.
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Hanjun Guo <guohanjun@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: dddc7ee3 ("perf probe: Fix an error when deleting probes successfully")
Link: http://lkml.kernel.org/r/1489738592-61011-1-git-send-email-wangkefeng.wang@huawei.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-probe.c

@@ -442,9 +442,9 @@ static int perf_del_probe_events(struct strfilter *filter)
 	}
 
 	if (ret == -ENOENT && ret2 == -ENOENT)
-		pr_debug("\"%s\" does not hit any event.\n", str);
-		/* Note that this is silently ignored */
-	ret = 0;
+		pr_warning("\"%s\" does not hit any event.\n", str);
+	else
+		ret = 0;
 
 error:
 	if (kfd >= 0)