Move the target_disas() m68k specifics to the CPUClass::disas_set_info()
hook and delete the #ifdef specific code in disas.c.

Signed-off-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Andreas Färber <afaerber@suse.de>