perf tests: Give a bit more information on the CQM test failure path

Before:

  $ perf test -v cqm
  48: Test intel cqm nmi context read                          :
  --- start ---
  test child forked, pid 1681
  parse_events failed
  test child finished with -2
  ---- end ----
  Test intel cqm nmi context read: Skip
  $

After:

  $ perf test -v cqm
  48: Test intel cqm nmi context read                          :
  --- start ---
  test child forked, pid 1681
  parse_events failed, is "intel_cqm/llc_occupancy/" available?
  test child finished with -2
  ---- end ----
  Test intel cqm nmi context read: Skip
  $

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Matt Fleming <matt.fleming@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-eidpiv5x4nkbsx37xwikbnir@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/arch/x86/tests/intel-cqm.c

@@ -54,7 +54,7 @@ int test__intel_cqm_count_nmi_context(int subtest __maybe_unused)
 
 	ret = parse_events(evlist, "intel_cqm/llc_occupancy/", NULL);
 	if (ret) {
-		pr_debug("parse_events failed\n");
+		pr_debug("parse_events failed, is \"intel_cqm/llc_occupancy/\" available?\n");
 		err = TEST_SKIP;
 		goto out;
 	}