m68k: use mmu fpu.h for non-mmu builds as well

None of the currently support m68knommu targets have an FPU.
Use the mmu version of fpu.h for all m68k.

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