m68k: remove the unused arch/m68k/platform directory

The non-mmu platform/machine directories have been move up one level.
We no longer need arch/m68k/platform, or its Makefile, so remove them.
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>

arch/m68k/platform/Makefile

-#
-# Makefile for the arch/m68knommu/platform.
-#