iommufd: Set domain->iommufd_hwpt in all hwpt->domain allocators

Setting domain->iommufd_hwpt in iommufd_hwpt_alloc() only covers the HWPT
allocations from user space, but not for an auto domain. This resulted in
a NULL pointer access in the auto domain pathway:
 Unable to handle kernel NULL pointer dereference at
 	virtual address 0000000000000008
 pc : iommufd_sw_msi+0x54/0x2b0
 lr : iommufd_sw_msi+0x40/0x2b0
 Call trace:
  iommufd_sw_msi+0x54/0x2b0 (P)
  iommu_dma_prepare_msi+0x64/0xa8
  its_irq_domain_alloc+0xf0/0x2c0
  irq_domain_alloc_irqs_parent+0x2c/0xa8
  msi_domain_alloc+0xa0/0x1a8

Since iommufd_sw_msi() requires to access the domain->iommufd_hwpt, it is
better to set that explicitly prior to calling iommu_domain_set_sw_msi().

Fixes: 748706d7 ("iommu: Turn fault_data to iommufd private pointer")
Link: https://patch.msgid.link/r/20250305211800.229465-1-nicolinc@nvidia.com


Reported-by: Ankit Agrawal <ankita@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Ankit Agrawal <ankita@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>