perf/ftrace: Small cleanup

ops->flags _should_ be 0 at this point, so setting the flag using
bitwise or is a bit daft.

Link: http://lkml.kernel.org/r/20171011080224.315585202@infradead.org

Requested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace_event_perf.c

@@ -363,7 +363,7 @@ static int perf_ftrace_function_register(struct perf_event *event)
 {
 	struct ftrace_ops *ops = &event->ftrace_ops;
 
-	ops->flags   |= FTRACE_OPS_FL_RCU;
+	ops->flags   = FTRACE_OPS_FL_RCU;
 	ops->func    = perf_ftrace_function_call;
 	ops->private = (void *)(unsigned long)nr_cpu_ids;