perf header: Fix a typo on evsel

For checking return value of the strdup, 'event' should be 'evsel'.
Signed-off-by: NNamhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1346897446-16569-1-git-send-email-namhyung@kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/header.c

@@ -2307,7 +2307,7 @@ static int perf_evsel__set_tracepoint_name(struct perf_evsel *evsel,
 
 	snprintf(bf, sizeof(bf), "%s:%s", event->system, event->name);
 	evsel->name = strdup(bf);
-	if (event->name == NULL)
+	if (evsel->name == NULL)
 		return -1;
 
 	evsel->tp_format = event;