m68knommu: support version 2 ColdFire split cache

The newer version 2 ColdFire CPU cores support a configurable cache
arrangement. The cache memory can be used as all instruction cache, all
data cache, or split in half for both instruction and data caching.
Support this setup via a Kconfig time menu that allows a kernel builder
to choose the arrangement they want to use.

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