dtc: Add a testcase for 'reg' or 'ranges' in /

This patch adds an extra testcase to dtc to ensure that the
"reg_format" and "ranges_format" checks trigger as they should if a
'reg' or 'ranges' property appears in the root node.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

tests/reg-ranges-root.dts

@@ -0,0 +1,8 @@
+/dts-v1/;
+
+/ {
+	#address-cells = <1>;
+	#size-cells = <1>;
+	reg = <0x1000 0x10>;
+	ranges = <0x1000 0x2000 0x1000>;
+};