[PATCH v5 08/13] iommufd/selftest: Prepare for mock_viommu_alloc_domain_nested()

[Tian, Kevin]

> From: Nicolin Chen <nicolinc at nvidia.com>
> Sent: Saturday, October 26, 2024 7:50 AM
> 
> A nested domain now can be allocated for a parent domain for a vIOMMU
> object. Rework the existing allocators to prepare for the latter case.
> 
> Signed-off-by: Nicolin Chen <nicolinc at nvidia.com>

Reviewed-by: Kevin Tian <kevin.tian at intel.com>