[POWERPC] Fix IO space on PCI buses created from of_platform

This changes the way of_platform_pci creates PCI host bridges such
that it uses request_phb_iospace() for mapping the IO ports, instead
of using the dynamic hotplug stuff.  That guarantees the IO space
stays within the 2GB limit and thus doesn't break half of the legacy
drivers around.

Fixes a couple of warnings due to missing IO space while at it.

This patch is a temporary workaround for 2.6.22 before a more complete
rewrite of IO mappings is merged in 2.6.23

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