[POWERPC] Fix pci_setup_phb_io_dynamic for pci_iomap

[POWERPC] Fix pci_setup_phb_io_dynamic for pci_iomap

We had a problem on a system with only dynamically allocated
PCI buses (using of_pci_phb_driver) in combination with libata.
This setup ended up having no "primary" phb, which means
that pci_io_base never got initialized and all IO port
numbers are 64 bit numbers, which is larger than the
PIO_MASK limit.

Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>