libperf: Move 'nr_groups' from tools/perf to evlist::nr_groups

Move evsel::nr_groups to perf_evsel::nr_groups, so we can move the group
interface to libperf.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Requested-by: Shunsuke Nakamura <nakamura.shun@fujitsu.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20210706151704.73662-5-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 6a8cc19..ee2a5ca 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1776,7 +1776,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 		rec->tool.ordered_events = false;
 	}
 
-	if (!rec->evlist->nr_groups)
+	if (!rec->evlist->core.nr_groups)
 		perf_header__clear_feat(&session->header, HEADER_GROUP_DESC);
 
 	if (data->is_pipe) {