m68knommu: remove ColdFire CLOCK_DIV config option

The reality is that you do not need the abiltity to configure the
clock divider for ColdFire CPUs. It is a fixed ratio on any given
ColdFire family member. It is not the same for all ColdFire parts,
but it is always the same in a model range. So hard define the divider
for each supported ColdFire CPU type and remove the Kconfig option.

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