s390/virtio_ccw: Fix dma_parm pointer not set up

At least since commit 334304ac2bac ("dma-mapping: don't return errors
from dma_set_max_seg_size") setting up device.dma_parms is basically
mandated by the DMA API. As of now Channel (CCW) I/O in general does not
utilize the DMA API, except for virtio. For virtio-ccw however the
common virtio DMA infrastructure is such that most of the DMA stuff
hinges on the virtio parent device, which is a CCW device.

So lets set up the dma_parms pointer for the CCW parent device and hope
for the best!

Fixes: 334304ac2bac ("dma-mapping: don't return errors from dma_set_max_seg_size")
Reported-by: Marc Hartmayer <[e-mail]>
Reviewed-by: Eric Farman <[e-mail]>
Reviewed-by: Cornelia Huck <[e-mail]>
Tested-by: Marc Hartmayer <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Halil Pasic <[e-mail]>
Signed-off-by: Heiko Carstens <[e-mail]>

drivers/s390/virtio/virtio_ccw.c

···
 	struct virtio_device vdev;
 	__u8 config[VIRTIO_CCW_CONFIG_SIZE];
 	struct ccw_device *cdev;
+	/* we make cdev->dev.dma_parms point to this */
+	struct device_dma_parameters dma_parms;
 	__u32 curr_io;
 	int err;
 	unsigned int revision; /* Transport revision */
···
 	unregister_virtio_device(&vcdev->vdev);
 	spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
 	dev_set_drvdata(&cdev->dev, NULL);
+	cdev->dev.dma_parms = NULL;
 	spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
 	return 0;
 }
···
 	}
 	vcdev->vdev.dev.parent = &cdev->dev;
 	vcdev->cdev = cdev;
+	cdev->dev.dma_parms = &vcdev->dma_parms;
 	vcdev->dma_area = ccw_device_dma_zalloc(vcdev->cdev,
 						sizeof(*vcdev->dma_area),
 						&vcdev->dma_area_addr);