iommu: Use __iommu_group_set_domain() for __iommu_attach_group()

iommu: Use __iommu_group_set_domain() for __iommu_attach_group()

The error recovery here matches the recovery inside
__iommu_group_set_domain(), so just use it directly.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/4-v5-1b99ae392328+44574-iommu_err_unwind_jgg@nvidia.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>