iommu/virtio: Drop IOVA cookie management

The core code bakes its own cookies now.

Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/f05cd2d0a0f414de3180e2536c7656faf1e52418.1628682049.git.robin.murphy@arm.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>