Migrate 5xxx boards from CONFIG_OF_FLAT_TREE to CONFIG_OF_LIBFDT

Affects boards: icecube (lite5200), jupiter, motionpro, tqm5200

Tested on: lite5200b

Note: the fixup functions have not been moved to a common place.  This
patch is targeted for immediate merging as in solves a build issue, but
the final name/location of the fixups is still subject to debate.  I
propose to merge this now, and move the fixups in the next merge window
to be usable by all targets.

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