block: remove per-queue plugging

Code has been converted over to the new explicit on-stack plugging,
and delay users have been converted to use the new API for that.
So lets kill off the old plugging along with aops->sync_page().

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index b9e1e15..5ef136c 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -394,7 +394,7 @@
 {
 	struct raid_set *rs = container_of(cb, struct raid_set, callbacks);
 
-	md_raid5_unplug_device(rs->md.private);
+	md_raid5_kick_device(rs->md.private);
 }
 
 /*