disas/m68k.c obviously belong to the m68k CPU section in
the MAINTAINERS file, but remove the hw/m68k/ directory
here since it only contains machine (not CPU) related
files, as requested by Laurent. Add the machine related
files to the right machine sections instead.

Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>