m68k: merge mmu and non-mmu versions of lib/Makefile

We can easily support the slight differences in libs needed by the
mmu and non-mmu builds in a single Makefile, so merge them back into
a single file again.

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