ARM: dts: mps2: remove skeleton.dtsi include and fix unit address warnings

Removale of skeleton.dtsi allows us also to fix the following
warning from the dts compiler:
  Warning (unit_address_vs_reg): Node /memory has a reg or ranges
  property, but no unit name

by adding proper unit addresses to the memory nodes.
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

arch/arm/boot/dts/mps2-an385.dts

@@ -59,7 +59,7 @@ chosen {
 		stdout-path = "serial0:9600n8";
 	};
 
-	memory {
+	memory@21000000 {
 		device_type = "memory";
 		reg = <0x21000000 0x1000000>;
 	};

arch/arm/boot/dts/mps2-an399.dts

@@ -59,7 +59,7 @@ chosen {
 		stdout-path = "serial0:9600n8";
 	};
 
-	memory {
+	memory@60000000 {
 		device_type = "memory";
 		reg = <0x60000000 0x1000000>;
 	};

arch/arm/boot/dts/mps2.dtsi

@@ -42,10 +42,12 @@
  *     OTHER DEALINGS IN THE SOFTWARE.
  */
 
-#include "skeleton.dtsi"
 #include "armv7-m.dtsi"
 
 / {
+	#address-cells = <1>;
+	#size-cells = <1>;
+
 	oscclk0: clk-osc0 {
 		compatible = "fixed-clock";
 		#clock-cells = <0>;