powerpc/5200: dts: rename nodes to prepare for refactoring dts files

This patch renames nodes in dts fils for MPC5200b files to prepare for
refactoring of these files later. When refactoring it will be easier to verify
the results if the node names aren't changing at the same time.

Signed-off-by: John Bonesio <bones@secretlab.ca>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>