test/py: use valid device tree in test_fit.py

The device tree compiler expects that a node with a unit-address has a reg
property.
Signed-off-by: NHeinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: NSimon Glass <sjg@chromium.org>

test/py/tests/test_fit.py

@@ -83,13 +83,16 @@ base_fdt = '''
 /dts-v1/;
 
 / {
-        model = "Sandbox Verified Boot Test";
-        compatible = "sandbox";
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	model = "Sandbox Verified Boot Test";
+	compatible = "sandbox";
 
 	reset@0 {
 		compatible = "sandbox,reset";
+		reg = <0>;
 	};
-
 };
 '''