binman: Adjust mkimage etype node reading

Since this is implemented as a section, it should really be split into
several functions, one to read the node and one to read the entries. Do
this so that it matches how Entry_section works.

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

tools/binman/etype/mkimage.py

@@ -45,11 +45,21 @@ class Entry_mkimage(Entry):
     """
     def __init__(self, section, etype, node):
         super().__init__(section, etype, node)
-        self._args = fdt_util.GetArgs(self._node, 'args')
         self._mkimage_entries = OrderedDict()
         self.align_default = None
+
+    def ReadNode(self):
+        super().ReadNode()
+        self._args = fdt_util.GetArgs(self._node, 'args')
         self.ReadEntries()
 
+    def ReadEntries(self):
+        """Read the subnodes to find out what should go in this image"""
+        for node in self._node.subnodes:
+            entry = Entry.Create(self, node)
+            entry.ReadNode()
+            self._mkimage_entries[entry.name] = entry
+
     def ObtainContents(self):
         # Use a non-zero size for any fake files to keep mkimage happy
         data, input_fname, uniq = self.collect_contents_to_file(
@@ -67,13 +77,6 @@ class Entry_mkimage(Entry):
 
         return True
 
-    def ReadEntries(self):
-        """Read the subnodes to find out what should go in this image"""
-        for node in self._node.subnodes:
-            entry = Entry.Create(self, node)
-            entry.ReadNode()
-            self._mkimage_entries[entry.name] = entry
-
     def SetAllowMissing(self, allow_missing):
         """Set whether a section allows missing external blobs