You can't change baudrate in this bootloader version. If you absolutely need to do this, then you can upgrade your bootloader to the new Caraboot. You can find the image at
https://github.com/8devices/Caraboot/tr ... er/release. I will make instructions for the upgrade procedure, this week (but hopefully tommorow) and post a link here. However please note that upgrading bootloader is very risky - if anything goes wrong, then your device won't work anymore.