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/include/configs/sandbox.h b/include/configs/sandbox.h
index 50affaf..5d75021 100644
--- a/include/configs/sandbox.h
+++ b/include/configs/sandbox.h
@@ -63,7 +63,11 @@
 	func(HOST, host, 1) \
 	func(HOST, host, 0)
 
+#ifdef __ASSEMBLY__
+#define BOOTENV
+#else
 #include <config_distro_bootcmd.h>
+#endif
 
 #define CONFIG_KEEP_SERVERADDR
 #define CONFIG_UDP_CHECKSUM