powerpc/powernv/iov: Don't add VFs to iommu group during PE config

In pnv_ioda_setup_vf_PE() we register an iommu group for the VF PE
then call pnv_ioda_setup_bus_iommu_group() to add devices to that group.
However, this function is called before the VFs are scanned so there's
no devices to add.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200406030745.24595-3-oohall@gmail.com