zynq: add memory nodes to device tree to initialize DRAM with OF

Commit 9e0e37ac added OF RAM initialization support
but memory nodes are missing in device tree.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Tested-by: Masahiro Yamada <yamada.m@jp.panasonic.com> [on ZC706 board]
Tested-by: Michal Simek <michal.simek@xilinx.com> [on ZC702 board]
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/arch/arm/dts/zynq-zed.dts b/arch/arm/dts/zynq-zed.dts
index 91a5deb..3488a56 100644
--- a/arch/arm/dts/zynq-zed.dts
+++ b/arch/arm/dts/zynq-zed.dts
@@ -11,4 +11,9 @@
 / {
 	model = "Zynq ZED Board";
 	compatible = "xlnx,zynq-zed", "xlnx,zynq-7000";
+
+	memory {
+		device_type = "memory";
+		reg = <0 0x20000000>;
+	};
 };