m68k: Kconfig.cpu: Fix indentation and add endif comments

The convention for indentation seems to be a single tab. Help text is
further indented by an additional two whitespaces. Fix the lines that
violate these rules.

While at it, add missing trailing endif comments and squeeze multiple
empty lines.

Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Link: https://lore.kernel.org/r/20220524075848.21684-2-juergh@canonical.com


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