85xx: Convert CONFIG_SYS_{PCI*,RIO*}_MEM_BASE to _MEM_BUS for FSL boards

Use CONFIG_SYS_{PCI,RIO}_MEM_BUS for the bus relative address instead
of _MEM_BASE so we are more explicit.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Andy Fleming <afleming@freescale.com>