iommu/terga: Do not use struct page as the handle for as->pd memory

Instead use the virtual address. Change from dma_map_page() to
dma_map_single() which works directly on a KVA. Add a type for the pd
table level for clarity.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/1-v4-c8663abbb606+3f7-iommu_pages_jgg@nvidia.com


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