iommupt: Add basic support for SW bits in the page table

iommupt: Add basic support for SW bits in the page table

SW bits can be placed on items, including table entries, single OA's and
individual items within a contiguous OA. They are guaranteed to be ignored
by the HW. The API is very basic since the only use case so far is a
single bit.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>