ppc: qemu: Support non-identity PCI bus address

ppc: qemu: Support non-identity PCI bus address

When QEMU originally supported the ppce500 machine back in Jan 2014,
it was created with a 1:1 mapping of PCI bus address. Things seemed
to change rapidly that in Nov 2014 with the following QEMU commits:

commit e6b4e5f4795b ("PPC: e500: Move CCSR and MMIO space to upper end of address space")

and

commit cb3778a0455a ("PPC: e500 pci host: Add support for ATMUs")

the PCI memory and IO physical address were moved to beyond 4 GiB,
but PCI bus address remained below 4 GiB, hence a non-identity
mapping was created. Unfortunately corresponding U-Boot updates
were missed along with the QEMU changes and the U-Boot QEMU ppce500
PCI support has been broken since then.

This commit makes the PCI (non-DM version) work again.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>