sandbox: Add a memory {} node

Add a memory node which indicates the size of sandbox memory.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sandbox/dts/sandbox64.dts b/arch/sandbox/dts/sandbox64.dts
index da2b442..37a5539 100644
--- a/arch/sandbox/dts/sandbox64.dts
+++ b/arch/sandbox/dts/sandbox64.dts
@@ -1,5 +1,7 @@
 /dts-v1/;
 
+#include <config.h>
+
 / {
 	#address-cells = <2>;
 	#size-cells = <2>;
@@ -13,6 +15,10 @@
 		spi0 = &spi;
 	};
 
+	memory {
+		reg = /bits/ 64 <0 CONFIG_SYS_SDRAM_SIZE>;
+	};
+
 	cros_ec: cros-ec {
 		reg = <0 0 0 0>;
 		u-boot,dm-pre-reloc;