m68k/atari: ROM port ISA adapter support

Atari ROM port ISA adapter support for EtherNEC and NetUSBee adapters

16 bit access for ROM port adapters follows debugging and
clarification by David Galvez <dgalvez75@gmail.com>. The NetUSBee
ISP1160 USB chip uses these macros.

Signed-off-by: Michael Schmitz <schmitz@debian.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>