[PATCH v2 08/14] iommufd/selftest: Drop parent domain from mock_iommu_domain_nested

[Tian, Kevin]

> From: Nicolin Chen <nicolinc at nvidia.com>
> Sent: Saturday, June 14, 2025 2:35 PM
> 
> There is no use of this parent domain. Delete the dead code.
> 
> Note that the s2_parent in struct mock_viommu will be a deadcode too. Yet,
> keep it because it will be soon used by HW queue objects, i.e. no point in
> adding it back and forth in such a short window. Besides, keeping it could
> cover the majority of vIOMMU use cases where a driver-level structure will
> be larger in size than the core structure.
> 
> Signed-off-by: Nicolin Chen <nicolinc at nvidia.com>

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