ARM: dts: imx53-voipac-dmm-668: Fix memory node duplication

imx53-voipac-dmm-668 has two memory nodes, but the correct representation
would be to use a single one with two reg entries - one for each RAM chip
select, so fix it accordingly.
Reported-by: NMarco Franchi <marco.franchi@nxp.com>
Signed-off-by: NFabio Estevam <festevam@gmail.com>
Signed-off-by: NMarco Franchi <marco.franchi@nxp.com>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx53-voipac-dmm-668.dtsi

@@ -17,12 +17,8 @@
 
 	memory@70000000 {
 		device_type = "memory";
-		reg = <0x70000000 0x20000000>;
-	};
-
-	memory@b0000000 {
-		device_type = "memory";
-		reg = <0xb0000000 0x20000000>;
+		reg = <0x70000000 0x20000000>,
+		      <0xb0000000 0x20000000>;
 	};
 
 	regulators {