of/promtree: add of_pdt namespace to pdt code

For symbols still lacking namespace qualifiers, add an of_pdt_ prefix.

Signed-off-by: Andres Salomon <dilinger@queued.net>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>