iommu: Set iommu_attach_handle->domain in core

iommu: Set iommu_attach_handle->domain in core

The IOMMU core sets the iommu_attach_handle->domain for the
iommu_attach_group_handle() path, while the iommu_replace_group_handle()
sets it on the caller side. Make the two paths aligned on it.

Link: https://patch.msgid.link/r/20240908114256.979518-3-yi.l.liu@intel.com
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>