vfio_noiommu_attach_group has two callers:

 1) __vfio_container_attach_groups is called by vfio_ioctl_set_iommu,
    which just called vfio_iommu_driver_allowed
 2) vfio_group_set_container requires already checks ->noiommu on the
    vfio_group, which is propagated from the iommudata in
    vfio_create_group

so this check is entirely superflous and can be removed.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20210924155705.4258-4-hch@lst.deSigned-off-by: Alex Williamson <alex.williamson@redhat.com>