iommu/amd: Drop IOVA cookie management

The core code bakes its own cookies now.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/648e74e7422caa6a7db7fb0c36813c7bd2007af8.1628682048.git.robin.murphy@arm.com


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