ARM: iop3xx: use fixed PCI i/o mapping

Move iop33x and iop32x PCI to fixed i/o mapping and remove io.h. This
changes the PCI bus addresses from the cpu address to 0 based. It appears
that there is translation h/w for this, but its untested.

Not sure what to do with io_offset. I think it should always be 0.
AFAICT, PCI setup is skipped if the ATU is already setup.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>