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

* Switched from 64M NOR/64M NAND to 4M NOR/256M NAND.
* Full DTM support including critical temperature.
* Added POST information.
* Removed LED function, moved to new LED driver.
* Moved ad7414 to new style I2C initialization.

Signed-off-by: Sean MacLennan <smaclennan@pikatech.com>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>