perf tools: Improve aux_output not supported error

For example:

 Before:
   $ perf record -e '{intel_pt/branch=0/,branch-loads/aux-output/ppp}' -- ls -l
   Error:
   branch-loads: PMU Hardware doesn't support sampling/overflow-interrupts. Try 'perf stat'

 After:
   $ perf record -e '{intel_pt/branch=0/,branch-loads/aux-output/ppp}' -- ls -l
   Error:
   branch-loads: PMU Hardware doesn't support 'aux_output' feature
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lore.kernel.org/lkml/20200710151104.15137-4-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evsel.c

@@ -2535,6 +2535,10 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target,
 	 "No such device - did you specify an out-of-range profile CPU?");
 		break;
 	case EOPNOTSUPP:
+		if (evsel->core.attr.aux_output)
+			return scnprintf(msg, size,
+	"%s: PMU Hardware doesn't support 'aux_output' feature",
+					 evsel__name(evsel));
 		if (evsel->core.attr.sample_period != 0)
 			return scnprintf(msg, size,
 	"%s: PMU Hardware doesn't support sampling/overflow-interrupts. Try 'perf stat'",