binman: fit: Set the image_pos attributes only once

The section etype has its own implementation of SetImagePos(), most of
which is not useful since the code is included here. So call
Entry.SetImagePos() which has the only piece of this which we actually
want.

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

tools/binman/etype/fit.py

@@ -894,7 +894,10 @@ class Entry_fit(Entry_section):
         """
         if self.build_done:
             return
-        super().SetImagePos(image_pos)
+
+        # Skip the section processing, since we do that below. Just call the
+        # entry method
+        Entry.SetImagePos(self, image_pos)
 
         # If mkimage is missing we'll have empty data,
         # which will cause a FDT_ERR_BADMAGIC error