m68knommu: remove use of MBAR value for ColdFire 523x peripheral addressing

The ColdFire 523x family of CPUs does not have an MBAR register, so don't
define its peripheral addresses relative to one. Its internal peripherals
are relative to the IPSBAR register, so make sure to use that.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>