perf: Fix perf probe build error

When we run into dry run mode, we want to make
write_kprobe_trace_event to succeed on writing the event. Let's
initialize it to 0.

Fixes the following build error:
	util/probe-event.c:1266: attention : «ret» may be used uninitialized in this function
	util/probe-event.c:1266: note: «ret» was declared here
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <1271808065-25290-1-git-send-regression-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/util/probe-event.c

@@ -1263,7 +1263,7 @@ static struct strlist *get_kprobe_trace_event_names(int fd, bool include_group)
 
 static int write_kprobe_trace_event(int fd, struct kprobe_trace_event *tev)
 {
-	int ret;
+	int ret = 0;
 	char *buf = synthesize_kprobe_trace_command(tev);
 
 	if (!buf) {