[POWERPC] Make pci_iounmap actually unmap things

This patch uses the newly added functions for testing if an address is
an ISA or PCI IO port to properly unmap things in pci_iounmap that
aren't such ports.  Without that, drivers using the iomap API will never
actually unmap resources, which on IBM server machines will prevent
hot-unplug of the corresponding HW adapters.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>