The commit introducing pcibios_io_space_offset() was ignoring 32-bit to
64-bit sign extention, which is the case on ppc32 with 64-bit resource
addresses. This only seems to have shown up while running under QEMU for
e500mc target. It may or may be suboptimal that QEMU has an IO base
address > 32-bits for the e500-pci implementation, but 1) it's still a
regression and 2) it's more correct to handle things this way.
Signed-off-by: Ben Collins <ben.c@servergy.com>