perf evlist: Fix set event list leader

The __perf_evlist__set_leader() was setting the leader for all events in
the list except the first. Which means it assumed the first event
already had event->leader = event.

Seems like this should be the role of the function to also do this. This
is a requirement for an upcoming patch set.
Signed-off-by: Stephane Eranian <eranian@google.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Tested-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20130131125437.GA3656@quadSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evlist.c

@@ -122,8 +122,7 @@ void __perf_evlist__set_leader(struct list_head *list)
 	leader->nr_members = evsel->idx - leader->idx + 1;
 
 	list_for_each_entry(evsel, list, node) {
-		if (evsel != leader)
-			evsel->leader = leader;
+		evsel->leader = leader;
 	}
 }