arm: mvebu: Fix memory size for Armada 370 DB

Actually the Armada 370 DB (aka DB-88F6710-BP-DDR3) come with 1GB and
not 512MB.
Signed-off-by: NGregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: NJason Cooper <jason@lakedaemon.net>

arch/arm/boot/dts/armada-370-db.dts

@@ -26,7 +26,7 @@
 
 	memory {
 		device_type = "memory";
-		reg = <0x00000000 0x20000000>; /* 512 MB */
+		reg = <0x00000000 0x40000000>; /* 1 GB */
 	};
 
 	soc {