[PATCH] Fix bug in md superblock sanity checking.

This call the super_90_load is meant to make sure that the new
superblock is consistant with a pre-exisitnig one (on rdev0)...  but
rdev0 was not passed :-(

drivers/md/md.c

@@ -1925,7 +1925,7 @@ static int add_new_disk(mddev_t * mddev, mdu_disk_info_t *info)
 		if (!list_empty(&mddev->disks)) {
 			mdk_rdev_t *rdev0 = list_entry(mddev->disks.next,
 							mdk_rdev_t, same_set);
-			int err = super_90_load(rdev, NULL);
+			int err = super_90_load(rdev, rdev0);
 			if (err < 0) {
 				printk(KERN_WARNING "md: %s has different UUID to %s\n",
 				       bdev_partition_name(rdev->bdev), bdev_partition_name(rdev0->bdev));