perf stat: Clear sample_(type|period) for counting

Clear sample_(type|period) for counting, as it only confuses debug
output with unwanted sampling details:

Before:

  $ sudo perf stat -e 'raw_syscalls:sys_enter' -vv ls
  ------------------------------------------------------------
  perf_event_attr:
    type                             2
    size                             112
    config                           0x11
    { sample_period, sample_freq }   1
    sample_type                      TIME|CPU|PERIOD|RAW
    read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
    disabled                         1
    inherit                          1
    enable_on_exec                   1
    exclude_guest                    1
  ...

After:
  $ sudo perf stat -e 'raw_syscalls:sys_enter' -vv ls
  ------------------------------------------------------------
  perf_event_attr:
    type                             2
    size                             112
    config                           0x11
    read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
    disabled                         1
    inherit                          1
    enable_on_exec                   1
    exclude_guest                    1
  ...

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1448465815-27404-1-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-stat.c

@@ -161,6 +161,13 @@ static int create_perf_stat_counter(struct perf_evsel *evsel)
 
 	attr->inherit = !no_inherit;
 
+	/*
+	 * Some events get initialized with sample_(period/type) set,
+	 * like tracepoints. Clear it up for counting.
+	 */
+	attr->sample_period = 0;
+	attr->sample_type   = 0;
+
 	if (target__has_cpu(&target))
 		return perf_evsel__open_per_cpu(evsel, perf_evsel__cpus(evsel));