powerpc/pci: Move hose_list and pci_address_to_pio to pci-common

move the definition of hose_list next to its hotplug spinlock.

create pcibios_io_size to encapsulate ifdef in existing pci-common
function pcibios_vaddr_is_ioport

move pci_address_to_pio to pci-common, using new pcibios_io_size, and
protect this GPL exported function against concurrent hotplug removal

Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>