block: unexport blkdev_ioctl

With the raw driver gone, there is no modular user left.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211012104450.659013-2-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/ioctl.c

@@ -588,7 +588,6 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
 		return -ENOTTY;
 	return bdev->bd_disk->fops->ioctl(bdev, mode, cmd, arg);
 }
-EXPORT_SYMBOL_GPL(blkdev_ioctl); /* for /dev/raw */
 
 #ifdef CONFIG_COMPAT