mpc8641: Make PCI and RIO mutually exclusive, fix non-PCI build

You can't actually have both, and with some coming changes to
change the memory map for the board and support 36-bit physical,
we need the extra BAT that is being consumed by having both.

I also make non-PCI configs build cleanly, for the sake of sanity.

Signed-off-by: Becky Bruce <becky.bruce@freescale.com>