libfdt: Add a test for fdt_getprop_by_offset()

This function does not have its own test at present. Add one.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
diff --git a/tests/run_tests.sh b/tests/run_tests.sh
index 23e6176..ca3fc86 100755
--- a/tests/run_tests.sh
+++ b/tests/run_tests.sh
@@ -303,6 +303,7 @@
     run_test path_offset $TREE
     run_test get_name $TREE
     run_test getprop $TREE
+    run_test get_prop_offset $TREE
     run_test get_phandle $TREE
     run_test get_path $TREE
     run_test supernode_atdepth_offset $TREE