Since it is now possible to instantiate a CPU and RAM with the "none"
machine, too, and a kernel can be loaded there with the generic loader
device, there is no more need for the m68k "dummy" machine. Thus let's
remove this unmaintained file now.

Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Thomas Huth <huth@tuxfamily.org>