powernv/pci: Fold pnv_pci_dma_dev_setup() into the pci-ioda.c version

pnv_pci_dma_dev_setup() does nothing but call the phb->dma_dev_setup()
callback, if one exists. That callback is only set for normal PCIe PHBs so
we can remove the layer of indirection and use the ioda version in
the pci_controller_ops.

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/20200110070207.439-5-oohall@gmail.com