[SCSI] bsg: fix bsg_register_queue error path

unfortunately, if IS_ERR(class_dev) is true, that means class_dev isn't
null and the check in the error leg is pointless ... it's also asking
for trouble to request unregistration of a device we haven't actually
created (although it works currently). Fix by using explicit gotos and
unregisters.

Acked-by: FUJITA Tomonori <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

block/bsg.c

···
 	if (q->kobj.sd) {
 		ret = sysfs_create_link(&q->kobj, &bcd->class_dev->kobj, "bsg");
 		if (ret)
-			goto err;
+			goto err_unregister;
 	}
 
 	list_add_tail(&bcd->list, &bsg_class_list);
···
 
 	mutex_unlock(&bsg_mutex);
 	return 0;
+
+err_unregister:
+	class_device_unregister(class_dev);
 err:
-	if (class_dev)
-		class_device_destroy(bsg_class, MKDEV(bsg_major, bcd->minor));
 	mutex_unlock(&bsg_mutex);
 	return ret;
 }