m68knommu: fix ColdFire definition of CLOCK_TICK_RATE

The good definition of CLOCK_TICK_RATE for coldfires has been lost in the
merge of m68k and m68knommu include files.  Restore it.  Culprit :
commit ebafc174



Signed-off-by: Philippe De Muyter <phdm@macqel.be>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>