ring-buffer: rb_is_reader_page() can return boolean

Make rb_is_reader_page() return bool to improve readability due to this
particular function only using either true or false as its return value.

No functional change.

Link: http://lkml.kernel.org/r/1443537816-5788-4-git-send-email-bywxiaobai@163.comSigned-off-by: Yaowei Bai <bywxiaobai@163.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/ring_buffer.c

@@ -829,7 +829,7 @@ rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
  * writer is ever on it, the previous pointer never points
  * back to the reader page.
  */
-static int rb_is_reader_page(struct buffer_page *page)
+static bool rb_is_reader_page(struct buffer_page *page)
 {
 	struct list_head *list = page->list.prev;