test: create dedicated fdt node for ofnode_for_each_prop test

Property count may change in /buttons node, if more button tests added,
and this will break ofnode_for_each_prop.
Add separate node for mentioned test.

Signed-off-by: Dzmitry Sankouski <dsankouski@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/sandbox/dts/test.dts

@@ -1537,6 +1537,20 @@
 		};
 	};
 
+	ofnode-foreach {
+		compatible = "foreach";
+
+		first {
+			prop1 = <1>;
+			prop2 = <2>;
+		};
+
+		second {
+			prop1 = <1>;
+			prop2 = <2>;
+		};
+	};
+
 	osd {
 		compatible = "sandbox,sandbox_osd";
 	};

test/dm/ofnode.c

@@ -1046,7 +1046,7 @@ static int dm_test_ofnode_for_each_prop(struct unit_test_state *uts)
 	struct ofprop prop;
 	int count;
 
-	node = ofnode_path("/buttons");
+	node = ofnode_path("/ofnode-foreach");
 	count = 0;
 
 	/* we expect "compatible" for each node */