tools/mpy-tool.py: Include .py extension in frozen filename.

So that it can be correctly stat'd when looking for frozen files.

tools/mpy-tool.py

@@ -502,7 +502,7 @@ def freeze_mpy(qcfgs, base_qstrs, raw_codes):
     print()
     print('const char mp_frozen_mpy_names[] = {')
     for rc in raw_codes:
-        module_name = rc.source_file.str[:-len(".py")]
+        module_name = rc.source_file.str
         slash = module_name.rfind('/')
         if slash != -1:
             module_name = module_name[slash + 1:]