pci: mpc85xx: Do not try to access extended PCIe registers

Driver pci_mpc85xx.c is PCI controller driver for old PCI Local Bus,
which does not support access to extended PCIe registers (above 0xff),
as opposite of the PCIe driver pcie_fsl.c for the same platform.

So do not try to access extended PCIe registers as it cannot work.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Heiko Schocher <hs@denx.de>
Tested-by: Heiko Schocher <hs@denx.de>