perf evsel: Rename perf_evsel__group_desc() to evsel__group_desc()

As it is a 'struct evsel' method, not part of tools/lib/perf/, aka
libperf, to whom the perf_ prefix belongs.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index b5dd93a..e00f624 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -462,7 +462,7 @@ static size_t hists__fprintf_nr_sample_events(struct hists *hists, struct report
 	if (perf_evsel__is_group_event(evsel)) {
 		struct evsel *pos;
 
-		perf_evsel__group_desc(evsel, buf, size);
+		evsel__group_desc(evsel, buf, size);
 		evname = buf;
 
 		for_each_group_member(pos, evsel) {