m68knommu: move ColdFire slice timer address defiens to 54xx header

Move the base address defines of the ColdFire 54xx CPU slice timers into the
54xx specific header (m54xxsim.h). They are CPU specific, and belong with the
CPU specific defines. Also make them relative to the MBAR peripheral region,
making the define the absolute address.

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