block: nbd: convert to blkdev_reread_part()

Reviewed-by: Christoph Hellwig <[e-mail]>
Tested-by: Jarod Wilson <[e-mail]>
Acked-by: Jarod Wilson <[e-mail]>
Signed-off-by: Ming Lei <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

drivers/block/nbd.c

···
 		bdev->bd_inode->i_size = 0;
 		set_capacity(nbd->disk, 0);
 		if (max_part > 0)
-			ioctl_by_bdev(bdev, BLKRRPART, 0);
+			blkdev_reread_part(bdev);
 		if (nbd->disconnect) /* user requested, ignore socket errors */
 			return 0;
 		return nbd->harderror;