AioContext: correct comments

Correct comments of field notify_me

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Max Reitz <mreitz@redhat.com>
Signed-off-by: NCao jin <caoj.fnst@cn.fujitsu.com>
Message-id: 1468575858-22975-1-git-send-email-caoj.fnst@cn.fujitsu.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>

include/block/aio.h

@@ -74,7 +74,7 @@ struct AioContext {
      * event_notifier_set necessary.
      *
      * Bit 0 is reserved for GSource usage of the AioContext, and is 1
-     * between a call to aio_ctx_check and the next call to aio_ctx_dispatch.
+     * between a call to aio_ctx_prepare and the next call to aio_ctx_check.
      * Bits 1-31 simply count the number of active calls to aio_poll
      * that are in the prepare or poll phase.
      *