iommu/amd/io-pgtable: Implement unmap_pages io_pgtable_ops callback

Implement the io_pgtable_ops->unmap_pages() callback for AMD driver
and deprecate io_pgtable_ops->unmap callback.

Also if fetch_pte() returns NULL then return from unmap_mapages()
instead of trying to continue to unmap remaining pages.

Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Link: https://lore.kernel.org/r/20220825063939.8360-3-vasant.hegde@amd.com


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