dm: arm: Bring in skeleton64 device tree file from Linux

Backport of kernel commits:
	7c14f6c719de092d69c81877786e83ce7ae1a860
	35faad2a1563b3d4dc983a82ac41033fe053870c

Signed-off-by: Haikun Wang <Haikun.Wang@freescale.com>
Acked-by: Simon Glass <sjg@chromium.org>

arch/arm/dts/skeleton64.dtsi

@@ -0,0 +1,13 @@
+/*
+ * Skeleton device tree in the 64 bits version; the bare minimum
+ * needed to boot; just include and add a compatible value.  The
+ * bootloader will typically populate the memory node.
+ */
+
+/ {
+	#address-cells = <2>;
+	#size-cells = <2>;
+	chosen { };
+	aliases { };
+	memory { device_type = "memory"; reg = <0 0 0 0>; };
+};