[POWERPC] mpc5200: add #address-cells and #size-cells to soc node.

The various 5200 dts files don't have values specified for the soc
node, which in turn results in a warning from the processing of
every child node (roughly 40 warnings per file).  This explicitly
sets the default values and gets rid of all the warnings.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>