dtoc: Improve internal error for Refresh()

Add the node name too so it is easy to see which node failed.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/dtoc/fdt.py b/tools/dtoc/fdt.py
index 25ce513..f0d1384 100644
--- a/tools/dtoc/fdt.py
+++ b/tools/dtoc/fdt.py
@@ -339,8 +339,8 @@
             p = fdt_obj.get_property_by_offset(poffset)
             prop = self.props.get(p.name)
             if not prop:
-                raise ValueError("Internal error, property '%s' missing, "
-                                 'offset %d' % (p.name, poffset))
+                raise ValueError("Internal error, node '%s' property '%s' missing, "
+                                 'offset %d' % (self.path, p.name, poffset))
             prop.RefreshOffset(poffset)
             poffset = fdt_obj.next_property_offset(poffset, QUIET_NOTFOUND)