ARM: dts: kirkwood: Fix Openblock A6 nand partition overlap

The "test" and "conf" nand partitions partly overlap:

Creating 6 MTD partitions on "orion_nand":
0x000000000000-0x000000090000 : "uboot"
0x000000090000-0x0000000d4000 : "env"
0x0000000d4000-0x0000000f8000 : "test"
0x0000000f4000-0x0000004f4000 : "conf"

That is unlikely to be desired, and not matching the partition map used in
u-boot - So adjust the test partition size to fix this.
Signed-off-by: NPeter Korsgaard <peter@korsgaard.com>
Signed-off-by: NGregory CLEMENT <gregory.clement@free-electrons.com>

arch/arm/boot/dts/kirkwood-openblocks_a6.dts

@@ -141,7 +141,7 @@
 
 	partition@d4000 {
 		label = "test";
-		reg = <0xd4000 0x24000>;
+		reg = <0xd4000 0x20000>;
 	};
 
 	partition@f4000 {