binman: Allow entries to expand after packing

Add support for detecting entries that change size after they have already
been packed, and re-running packing when it happens.

This removes the limitation that entry size cannot change after
PackEntries() is called.

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

tools/binman/image.py

@@ -55,6 +55,10 @@ class Image:
             self._filename = filename
         self._section = bsection.Section('main-section', None, self._node, self)
 
+    def Raise(self, msg):
+        """Convenience function to raise an error referencing an image"""
+        raise ValueError("Image '%s': %s" % (self._node.path, msg))
+
     def GetFdtSet(self):
         """Get the set of device tree files used by this image"""
         return self._section.GetFdtSet()
@@ -100,6 +104,10 @@ class Image:
         """
         self._section.GetEntryOffsets()
 
+    def ResetForPack(self):
+        """Reset offset/size fields so that packing can be done again"""
+        self._section.ResetForPack()
+
     def PackEntries(self):
         """Pack all entries into the image"""
         self._section.PackEntries()