iommufd/selftest: Add IOMMU_TEST_OP_MD_CHECK_IOTLB test op

Allow to test whether IOTLB has been invalidated or not.

Link: https://lore.kernel.org/r/20240111041015.47920-6-yi.l.liu@intel.com
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>