m68k/atari: ARAnyM - Add support for block access

[geert: Cleanups and updates]

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Petr Stehlik <pstehlik@sophics.cz>