perf stat: Don't display zero tool counts

Andi reported (see link below) a regression when printing the
'duration_time' tool event, where it gets printed as "not counted" for
most of the CPUs, fix it by skipping zero counts for tool events.

Reported-by: Andi Kleen <[e-mail]>
Signed-off-by: Ian Rogers <[e-mail]>
Tested-by: Andi Kleen <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Athira Rajeev <[e-mail]>
Cc: Claire Jensen <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: https://lore.kernel.org/all/ZMlrzcVrVi1lTDmn@tassilo/
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/stat-display.c

···
 	 */
 	if (config->aggr_mode == AGGR_THREAD && config->system_wide)
 		return true;
+
+	/* Tool events have the software PMU but are only gathered on 1. */
+	if (evsel__is_tool(counter))
+		return true;
+
 	/*
 	 * Skip value 0 when it's an uncore event and the given aggr id
 	 * does not belong to the PMU cpumask.