Where appropriate, use the endian-flipping OF_getencprop() instead of
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