iommufd: Change the selftest to use iommupt instead of xarray

iommufd: Change the selftest to use iommupt instead of xarray

The iommufd self test uses an xarray to store the pfns and their orders to
emulate a page table. Make it act more like a real iommu driver by
replacing the xarray with an iommupt based page table. The new AMDv1 mock
format behaves similarly to the xarray.

Add set_dirty() as a iommu_pt operation to allow the test suite to
simulate HW dirty.

Userspace can select between several formats including the normal AMDv1
format and a special MOCK_IOMMUPT_HUGE variation for testing huge page
dirty tracking. To make the dirty tracking test work the page table must
only store exactly 2M huge pages otherwise the logic the test uses
fails. They cannot be broken up or combined.

Aside from aligning the selftest with a real page table implementation,
this helps test the iommupt code itself.

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>