brd: fix name argument of unregister_blkdev()

The name of brd block device is "ramdisk", it's not "brd".
(The block device is registered by register_blkdev(RAMDISK_MAJOR, "ramdisk")
So it should be unregistered by unregister_blkdev(RAMDISK_MAJOR, "ramdisk")

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/block/brd.c

@@ -571,8 +571,8 @@ out_free:
 		list_del(&brd->brd_list);
 		brd_free(brd);
 	}
+	unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
 
-	unregister_blkdev(RAMDISK_MAJOR, "brd");
 	return -ENOMEM;
 }