iommu: Make @handle mandatory in iommu_{attach|replace}_group_handle()

Caller of the two APIs always provide a valid handle, make @handle as
mandatory parameter. Take this chance incoporate the handle->domain
set under the protection of group->mutex in iommu_attach_group_handle().

Link: https://patch.msgid.link/r/20250226011849.5102-2-yi.l.liu@intel.com


Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>