MP3Decoder: ensure object uses finalizer

.. so that the underlying allocations will be freed. This is not
important now but will be if the underlying allocator is changed
to something else like `port_malloc` in the future.

Author: jepler

shared-bindings/audiomp3/MP3Decoder.c

@@ -94,7 +94,9 @@ STATIC mp_obj_t audiomp3_mp3file_make_new(const mp_obj_type_t *type, size_t n_ar
         arg = mp_call_function_2(MP_OBJ_FROM_PTR(&mp_builtin_open_obj), arg, MP_ROM_QSTR(MP_QSTR_rb));
     }
 
-    audiomp3_mp3file_obj_t *self = mp_obj_malloc(audiomp3_mp3file_obj_t, &audiomp3_mp3file_type);
+    audiomp3_mp3file_obj_t *self = m_new_obj_with_finaliser(audiomp3_mp3file_obj_t);
+    self->base.type = &audiomp3_mp3file_type;
+
     if (!mp_obj_is_type(arg, &mp_type_fileio)) {
         mp_raise_TypeError(MP_ERROR_TEXT("file must be a file opened in byte mode"));
     }
@@ -260,6 +262,7 @@ STATIC const mp_rom_map_elem_t audiomp3_mp3file_locals_dict_table[] = {
     // Methods
     { MP_ROM_QSTR(MP_QSTR_open), MP_ROM_PTR(&audiomp3_mp3file_open_obj) },
     { MP_ROM_QSTR(MP_QSTR_deinit), MP_ROM_PTR(&audiomp3_mp3file_deinit_obj) },
+    { MP_ROM_QSTR(MP_QSTR___del__), MP_ROM_PTR(&audiomp3_mp3file_deinit_obj) },
     { MP_ROM_QSTR(MP_QSTR___enter__), MP_ROM_PTR(&default___enter___obj) },
     { MP_ROM_QSTR(MP_QSTR___exit__), MP_ROM_PTR(&audiomp3_mp3file___exit___obj) },