iommu/sun50i: Add an IOMMU_IDENTITIY_DOMAIN

Prior to commit 1b932ced ("iommu: Remove detach_dev callbacks") the
sun50i_iommu_detach_device() function was being called by
ops->detach_dev().

This is an IDENTITY domain so convert sun50i_iommu_detach_device() into
sun50i_iommu_identity_attach() and a full IDENTITY domain and thus hook it
back up the same was as the old ops->detach_dev().

Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/19-v8-81230027b2fa+9d-iommu_all_defdom_jgg@nvidia.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>