iommupt: Add a mock pagetable format for iommufd selftest to use

iommupt: Add a mock pagetable format for iommufd selftest to use

The iommufd self test uses an xarray to store the pfns and their orders to
emulate a page table. Slightly modify the amdv1 page table to create a
real page table that has similar properties:

 - 2k base granule to simulate something like a 4k page table on a 64K
   PAGE_SIZE ARM system
 - Contiguous page support for every PFN order
 - Dirty tracking

AMDv1 is the closest format, as it is the only one that already supports
every page size. Tweak it to have only 5 levels and an 11 bit base granule
and compile it separately as a format variant.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Tested-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Tested-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>