dtoc: Allow adding variable-sized data to a dtb

Add a method for adding a property containing arbitrary bytes. Make sure
that the tree can expand as needed in this case.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/dtoc/test_fdt.py

@@ -417,6 +417,10 @@ class TestProp(unittest.TestCase):
         self.node.SetData('empty', b'123')
         self.assertEqual(b'123', prop.bytes)
 
+        # Trying adding a lot of data at once
+        self.node.AddData('data', tools.GetBytes(65, 20000))
+        self.dtb.Sync(auto_resize=True)
+
     def testFromData(self):
         dtb2 = fdt.Fdt.FromData(self.dtb.GetContents())
         self.assertEqual(dtb2.GetContents(), self.dtb.GetContents())