Revert "powerpc/85xx: p2020rdb - move the NAND address."

This reverts commit 0c00f656.
The initial commit was my fault. There are two boards out there:
P2020RDB and P2020RDB-PC. I wasn't aware of that and assumed that I have
a RDB board in front of me while I the RDB-PC. This patch makes it work
for the RDB-PC variant and breaks it for the RDB. Now there is a device
tree file available for the RDB-PC which was not there earlier. So with
this revert, everything gets back to normal :)

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>