m68knommu: make ColdFire 5249 MBAR2 register definitions absolute addresses

Make the ColdFire 5249 MBAR peripheral register definitions absolute
addresses, instead of offsets into the region.

The various ColdFire parts use different methods to address the internal
registers, some are absolute, some are relative to peripheral regions
which can be mapped at different address ranges (such as the MBAR and IPSBAR
registers). We don't want to deal with this in the code when we are
accessing these registers, so make all register definitions the absolute
address - factoring out whether it is an offset into a peripheral region.

This makes them all consistently defined, and reduces the occasional bugs
caused by inconsistent definition of the register addresses.

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