perf evsel: Rename perf_evsel__is_*() to evsel__is*()

As those are 'struct evsel' methods, 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>

tools/perf/ui/gtk/annotate.c

@@ -130,7 +130,7 @@ static int perf_gtk__annotate_symbol(GtkWidget *window, struct map_symbol *ms,
 
 		gtk_list_store_append(store, &iter);
 
-		if (perf_evsel__is_group_event(evsel)) {
+		if (evsel__is_group_event(evsel)) {
 			for (i = 0; i < evsel->core.nr_members; i++) {
 				ret += perf_gtk__get_percent(s + ret,
 							     sizeof(s) - ret,

tools/perf/ui/gtk/hists.c

@@ -642,7 +642,7 @@ int perf_evlist__gtk_browse_hists(struct evlist *evlist,
 		size_t size = sizeof(buf);
 
 		if (symbol_conf.event_group) {
-			if (!perf_evsel__is_group_leader(pos))
+			if (!evsel__is_group_leader(pos))
 				continue;
 
 			if (pos->core.nr_members > 1) {