binman: Adjust Entry to read the node in a separate call

At present the Entry constructor sets up the object and then immediately
reads its device-tree node to obtain its properties.

This breaks a convention that constructors should not do any processing.
A consequence is that we must pass all arguments to the constructor and
cannot have the node-reading proceed in a different way unless we pass
flags to that constructor. We already have a 'test' flag in a few cases,
and now need to control whether the 'orig_offset' and 'orig_size'
properties are set or not.

Adjust the code to require a separate call to ReadNode() after
construction. The Image class remains as it was.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/entry_test.py b/tools/binman/entry_test.py
index 460171b..ee729f3 100644
--- a/tools/binman/entry_test.py
+++ b/tools/binman/entry_test.py
@@ -57,7 +57,7 @@
     def testEntryContents(self):
         """Test the Entry bass class"""
         import entry
-        base_entry = entry.Entry(None, None, None, read_node=False)
+        base_entry = entry.Entry(None, None, None)
         self.assertEqual(True, base_entry.ObtainContents())
 
     def testUnknownEntry(self):
@@ -73,15 +73,15 @@
         """Test Entry.GetUniqueName"""
         Node = collections.namedtuple('Node', ['name', 'parent'])
         base_node = Node('root', None)
-        base_entry = entry.Entry(None, None, base_node, read_node=False)
+        base_entry = entry.Entry(None, None, base_node)
         self.assertEqual('root', base_entry.GetUniqueName())
         sub_node = Node('subnode', base_node)
-        sub_entry = entry.Entry(None, None, sub_node, read_node=False)
+        sub_entry = entry.Entry(None, None, sub_node)
         self.assertEqual('root.subnode', sub_entry.GetUniqueName())
 
     def testGetDefaultFilename(self):
         """Trivial test for this base class function"""
-        base_entry = entry.Entry(None, None, None, read_node=False)
+        base_entry = entry.Entry(None, None, None)
         self.assertIsNone(base_entry.GetDefaultFilename())
 
     def testBlobFdt(self):