MD: change the parameter of md thread

Change the thread parameter, so the thread can carry extra info. Next patch
will use it.

Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index adda94d..81c02d6 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4625,8 +4625,9 @@
  * During the scan, completed stripes are saved for us by the interrupt
  * handler, so that they will not have to wait for our next wakeup.
  */
-static void raid5d(struct mddev *mddev)
+static void raid5d(struct md_thread *thread)
 {
+	struct mddev *mddev = thread->mddev;
 	struct r5conf *conf = mddev->private;
 	int handled;
 	struct blk_plug plug;