virtio_blk: ioctl return value fix

Block driver ioctl methods must return ENOTTY and not -ENOIOCTLCMD if
they expect the block layer to handle generic ioctls.

This triggered a BLKROSET failure in xfsqa #200.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/block/virtio_blk.c

@@ -213,7 +213,7 @@ static int virtblk_ioctl(struct block_device *bdev, fmode_t mode,
 	 * Only allow the generic SCSI ioctls if the host can support it.
 	 */
 	if (!virtio_has_feature(vblk->vdev, VIRTIO_BLK_F_SCSI))
-		return -ENOIOCTLCMD;
+		return -ENOTTY;
 
 	return scsi_cmd_ioctl(disk->queue, disk, mode, cmd, argp);
 }