m68k: Kconfig.machine: Add endif comment

Add missing trailing endif comment.

Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Link: https://lore.kernel.org/r/20220524075848.21684-4-juergh@canonical.com


Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>