bcache: fix ioctl in flash device

When doing ioctl in flash device, it will call ioctl_dev() in super.c,
then we should not to get cached device since flash only device has
no backend device. This patch just move the jugement dc->io_disable
to cached_dev_ioctl() to make ioctl in flash device correctly.

Fixes: 0f0709e6bfc3c ("bcache: stop bcache device when backing device is offline")
Signed-off-by: Tang Junhui <[e-mail]>
Cc: [e-mail]
Signed-off-by: Coly Li <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

drivers/md/bcache/request.c

···
 {
 	struct cached_dev *dc = container_of(d, struct cached_dev, disk);
 
+	if (dc->io_disable)
+		return -EIO;
+
 	return __blkdev_driver_ioctl(dc->bdev, mode, cmd, arg);
 }
 

drivers/md/bcache/super.c

···
 		     unsigned int cmd, unsigned long arg)
 {
 	struct bcache_device *d = b->bd_disk->private_data;
-	struct cached_dev *dc = container_of(d, struct cached_dev, disk);
-
-	if (dc->io_disable)
-		return -EIO;
 
 	return d->ioctl(d, mode, cmd, arg);
 }