m68knommu: remove use of MBAR in old-style ColdFire timer

Not all ColdFire CPUs that use the old style timer hardware module use
an MBAR set peripheral region. Move the TIMER base address defines to the
per-CPU header files where we can set it correctly based on how the
peripherals are mapped - instead of using a fake MBAR for some platforms.

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