arm64: dts: imx8mm: Memory node should be in board DT

Memory address/size depends on board design, so memory node should
be in board DT.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm-evk.dts

@@ -16,6 +16,11 @@ chosen {
 		stdout-path = &uart2;
 	};
 
+	memory@40000000 {
+		device_type = "memory";
+		reg = <0x0 0x40000000 0 0x80000000>;
+	};
+
 	leds {
 		compatible = "gpio-leds";
 		pinctrl-names = "default";

arch/arm64/boot/dts/freescale/imx8mm.dtsi

@@ -140,11 +140,6 @@ opp-1800000000 {
 		};
 	};
 
-	memory@40000000 {
-		device_type = "memory";
-		reg = <0x0 0x40000000 0 0x80000000>;
-	};
-
 	osc_32k: clock-osc-32k {
 		compatible = "fixed-clock";
 		#clock-cells = <0>;