iommu/vt-d: Do not wipe out the page table NID when devices detach

iommu/vt-d: Do not wipe out the page table NID when devices detach

The NID is used to control which NUMA node memory for the page table is
allocated it from. It should be a permanent property of the page table
when it was allocated and not change during attach/detach of devices.

Reviewed-by: Wei Wang <wei.w.wang@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/3-v3-dbbe6f7e7ae3+124ffe-vtd_prep_jgg@nvidia.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Fixes: 7c204426b818 ("iommu/vt-d: Add domain_alloc_paging support")
Link: https://lore.kernel.org/r/20250714045028.958850-6-baolu.lu@linux.intel.com
Signed-off-by: Will Deacon <will@kernel.org>