iommu/io-pgtable: Add DART pagetable format

Apple's DART iommu uses a pagetable format that shares some
similarities with the ones already implemented by io-pgtable.c.
Add a new format variant to support the required differences
so that we don't have to duplicate the pagetable handling code.

Reviewed-by: Alexander Graf <graf@amazon.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Sven Peter <sven@svenpeter.dev>
Link: https://lore.kernel.org/r/20210803121651.61594-2-sven@svenpeter.dev


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