perf test: Skip reason for suites with 1 test

When a suite has just 1 subtest, the subtest number is given as -1 to
avoid indented printing. When this subtest number is seen for the skip
reason, use the reason of the first test.
Reviewed-by: John Garry <john.garry@huawei.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Carsten Haitzler <carsten.haitzler@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Riccardo Mancini <rickyman7@gmail.com>
Cc: Sohaib Mohamed <sohaib.amhmd@gmail.com>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20220518042027.836799-2-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/builtin-test.c

@@ -137,10 +137,10 @@ static bool has_subtests(const struct test_suite *t)
 
 static const char *skip_reason(const struct test_suite *t, int subtest)
 {
-	if (t->test_cases && subtest >= 0)
-		return t->test_cases[subtest].skip_reason;
-
+	if (!t->test_cases)
 		return NULL;
+
+	return t->test_cases[subtest >= 0 ? subtest : 0].skip_reason;
 }
 
 static const char *test_description(const struct test_suite *t, int subtest)