m68knommu: remove use of MBAR value for ColdFire 528x peripheral addressing

The ColdFire 528x 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>