[POWERPC] PIKA Warp: Update DTS to support Rev B boards

* Switched from 64M NOR/64M NAND to 4M NOR/256M NAND.
* Added led entries.
* Added fpga-sd entry.
* Added ad7414 entry.

Signed-off-by: Sean MacLennan <smaclennan@pikatech.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>