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

There is only trivial differences between the non-mmu and mmu
versions of scatterlist.h. So use the mmu one and remove the non-mmu one.

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