ARM: dts: imx50: Fix memory node duplication

imx50-evk has duplicate memory nodes:

- One coming from the board dts file: memory@

- One coming from the imx50.dtsi file.

Fix the duplication by removing the memory node from the dtsi file
and by adding 'device_type = "memory";' in the board dts.
Reported-by: NRob Herring <robh@kernel.org>
Signed-off-by: NFabio Estevam <festevam@gmail.com>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx50-evk.dts

@@ -12,6 +12,7 @@
 	compatible = "fsl,imx50-evk", "fsl,imx50";
 
 	memory@70000000 {
+		device_type = "memory";
 		reg = <0x70000000 0x80000000>;
 	};
 };

arch/arm/boot/dts/imx50.dtsi

@@ -22,10 +22,8 @@
 	 * The decompressor and also some bootloaders rely on a
 	 * pre-existing /chosen node to be available to insert the
 	 * command line and merge other ATAGS info.
-	 * Also for U-Boot there must be a pre-existing /memory node.
 	 */
 	chosen {};
-	memory { device_type = "memory"; };
 
 	aliases {
 		ethernet0 = &fec;