perf tests: Fix Tool PMU test segfault

tool_pmu__event_to_str() now handles skipped events by returning NULL,
so it's wrong to re-check for a skip on the resulting string. Calling
tool_pmu__skip_event() with a NULL string results in a segfault so
remove the unnecessary skip to fix it:

$ perf test -vv "parsing with PMU name"

12.2: Parsing with PMU name:
...
---- unexpected signal (11) ----
12.2: Parsing with PMU name : FAILED!

Fixes: ee8aef2d2321 ("perf tools: Add skip check in tool_pmu__event_to_str()")
Signed-off-by: James Clark <[e-mail]>
Reported-by: Athira Rajeev <[e-mail]>
Acked-by: Kan Liang <[e-mail]>
Tested-by: Ian Rogers <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Namhyung Kim <[e-mail]>

tools/perf/tests/tool_pmu.c

···
 	parse_events_error__init(&err);
 	ret = parse_events(evlist, str, &err);
 	if (ret) {
-		if (tool_pmu__skip_event(tool_pmu__event_to_str(ev))) {
+		if (!tool_pmu__event_to_str(ev)) {
 			ret = TEST_OK;
 			goto out;
 		}
···
 		}
 	}
 
-	if (!found && !tool_pmu__skip_event(tool_pmu__event_to_str(ev))) {
+	if (!found && tool_pmu__event_to_str(ev)) {
 		pr_debug("FAILED %s:%d Didn't find tool event '%s' in parsed evsels\n",
 			 __FILE__, __LINE__, str);
 		ret = TEST_FAIL;