Clean up pdt.c:
 - make build dependent upon config OF_PROMTREE
 - #ifdef out the sparc-specific stuff
 - create pdt-specific header
Signed-off-by: NAndres Salomon <dilinger@queued.net>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>