arm: versatile: fix and enable PCI I/O space

With commit 4d5fc58d (ARM: remove bunch of now unused
mach/io.h files), the I/O space setup was completely broken on
versatile. This patch fixes that and prepares for further
I/O space clean-up.

I/O space handling on the versatile platform is currently
broken in multiple ways. Most importantly, the ports do
not get mapped into the virtual address space at all.

Also, there is some amount of confusion between PCI I/O
space and other statically mapped MMIO registers in the
platform code:

* The __io_address() macro that is used to access the
  platform register maps to the same __io macro that gets
  used for I/O space.

* The IO_SPACE_LIMIT is set to a value that is much larger
  than the total available space.

* The I/O resource of the PCI bus is set to the physical
  address of the mapping, which is way outside of the
  actual I/O space limit as well as the address range that
  gets decoded by traditional PCI cards.

* No attempt is made to stay outside of the ISA port range
  that some device drivers try access.

* No resource gets requested as a child of ioport_resource,
  but an IORESOURCE_IO type mapping gets requested
  as a child of iomem_resource.

This patch attempts to correct all of the above. This makes
it possible to use virtio-pci based virtual devices as well
as actual PCI cards including those with legacy ISA port
ranges like VGA.

Some of the issues seem to be duplicated on other platforms.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
[rob: update to 3.5-rc2 and io.h cleanup related changes]
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Tested-by: Robert Schwebel <r.schwebel@pengutronix.de>
Signed-off-by: Olof Johansson <olof@lixom.net>