tracing: Only call pipe_close if pipe_close is defined

This fixes a cut and paste error that had pipe_close get called
if pipe_open was defined (not pipe_close).
Reported-by: NKosaki Motohiro <kosaki.motohiro@jp.fujitsu.com>
LKML-Reference: <20091209153204.F4CD.A69D9226@jp.fujitsu.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

kernel/trace/trace.c

@@ -2899,7 +2899,7 @@ static int tracing_release_pipe(struct inode *inode, struct file *file)
 		cpumask_clear_cpu(iter->cpu_file, tracing_reader_cpumask);
 
 
-	if (iter->trace->pipe_open)
+	if (iter->trace->pipe_close)
 		iter->trace->pipe_close(iter);
 
 	mutex_unlock(&trace_types_lock);