m68k: use mmu kmap_types.h for non-mmu setups as well

The mmu version of kmap_types.h is identical to the non-mmu one.
Revert to a single file.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>