m68knommu: remove MBAR and IPSBAR hacks for the ColdFire 520x CPUs

The ColdFire 5207 and 5208 CPUs have fixed peripheral addresses.
They do not use the setable peripheral address registers like the MBAR
and IPSBAR used on many other ColdFire parts. Don't use fake values
of MBAR and IPSBAR when using peripheral addresses for them, there
is no need to.

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