tools/mpy-tool.py: Fix static qstrs when freezing without qstr header.

It's rare to freeze .mpy files without specifying a qstr header from a
firmware build, but it can be useful for testing, eg
`mpy-tool.py -f test.mpy`.  Fix this case so static qstrs are properly
excluded from the frozen qstr list.

Signed-off-by: Damien George <damien@micropython.org>

tools/mpy-tool.py

@@ -1795,7 +1795,7 @@ def main():
  else:
  config.MICROPY_QSTR_BYTES_IN_LEN = 1
  config.MICROPY_QSTR_BYTES_IN_HASH = 1
- firmware_qstr_idents = set(qstrutil.static_qstr_list)
+ firmware_qstr_idents = set(qstrutil.static_qstr_list_ident)
 
  # Create initial list of global qstrs.
  global_qstrs = GlobalQStrList()