docs: def flash_size_bytes(size):
      """ Given a flash size of the type passed in args.flash_size
      (ie 512KB or 1MB) then return the size in bytes.
      """
      if "MB" in size:
          return int(size[:size.index("MB")]) * 1024 * 1024
      elif "KB" in size:
          return int(size[:size.index("KB")]) * 1024
      else:
          raise FatalError("Unknown size %s" % size)