Wrong description QStorageInfo

Wrong qstorageinfo description  there are 1024MB (megabytes) in one GB (gigabyte)

```QStorageInfo storage = QStorageInfo::root();

    qDebug() << storage.rootPath();
    if (storage.isReadOnly())
        qDebug() << "isReadOnly:" << storage.isReadOnly();

    qDebug() << "name:" << storage.name();
    qDebug() << "fileSystemType:" << storage.fileSystemType();
    qDebug() << "size:" << storage.bytesTotal()/1000/1000 << "MB";
    qDebug() << "availableSize:" << storage.bytesAvailable()/1000/1000 << "MB";

```

replace 1000 to 1024