better on ofppc. In doing so, we also move a few functions around in
macppc and the generic ofw powerpc stuff to allow better sharing of code.
Also, introduce a model_init function.
move ofb_cons.c from macppc/dev to powerpc/oea and rename it to rascons.
This gets rid of some naming confusion, and makes it OFW-MI rather than
macppc specific.
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