Move mempak filestorage to readonly (handled via libretro)

mupen64plus-core/src/main/main.c

@@ -1477,7 +1477,7 @@ m64p_error main_run(void)
                     mpk_storages[i].size = MEMPAK_SIZE;
                     mpk_storages[i].filename = (void*)&mpk; /* OK for isubfile_storage */
 
-                    init_mempak(&g_dev.mempaks[i], &mpk_storages[i], &g_isubfile_storage);
+                    init_mempak(&g_dev.mempaks[i], &mpk_storages[i], &g_ifile_storage_ro);
                     l_paks[i][k] = &g_dev.mempaks[i];
 
                     if (Controls[i].Plugin == PLUGIN_MEMPAK) {