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

It is not at 0xffa00000. According to current u-boot source the NAND
controller is always at 0xff800000 and it is either at CS0 or CS1
depending on NAND or NAND+NOR mode. In 36bit mode it is shifted to
0xfff800000 but it has always an eight there and never an A.
Signed-off-by: NSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>

arch/powerpc/boot/dts/p2020rdb.dts

@@ -34,7 +34,7 @@
 
 		/* NOR and NAND Flashes */
 		ranges = <0x0 0x0 0x0 0xef000000 0x01000000
-			  0x1 0x0 0x0 0xffa00000 0x00040000
+			  0x1 0x0 0x0 0xff800000 0x00040000
 			  0x2 0x0 0x0 0xffb00000 0x00020000>;
 
 		nor@0,0 {