trace-cmd read: Fix --boundary option

The boundary option would only show boundaries for CPU 0, because
the boundary check looked at a hard coded CPU 0 page.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/trace-input.c b/trace-input.c
index 9380591..be25396 100644
--- a/trace-input.c
+++ b/trace-input.c
@@ -2475,7 +2475,7 @@
 				    struct pevent_record *record)
 {
 	struct page *page = record->priv;
-	struct kbuffer *kbuf = handle->cpu_data[0].kbuf;
+	struct kbuffer *kbuf = handle->cpu_data[record->cpu].kbuf;
 	int offset;
 
 	if (!page || !kbuf)