OF_getprop() to get encode-int encoded values from the OF tree. This is
a no-op at present, since all existing PowerPC ports are big-endian, but
it is a correctness improvement and will be required if we have a
little-endian kernel at some future point.
Where it is totally impossible for the code ever to be used on a
little-endian system (much of powerpc/powermac, for instance), I have not
necessarily made the appropriate changes.
MFC after: 1 month
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