The way to fix this quickly is to use a different machine, and this very thing is the reason that BIOS and firmware updates come with a warning (usually a big, colorful one) not to power them system off during the update.
If it's even possible to recover the system from this (and it might not be), you'll need to find the recovery BIOS version, and BIOS recovery instructions from the system or mainboard manufacturer. It's usually a pretty involved process, and to give you an idea of what you'd be in for, here's the page I've got for if I ever need to do a BIOS recovery on one of my home computers (which, obviously, has an Intel-built motherboard).
Fun times, huh? I always shudder when I read something like:
Open the chassis and remove the BIOS Configuration Jumper. See the Technical Product Specification for details including the location of this jumper.
Since you haven't specified who manufactured this system, that's all the help we'll be able to give.
Good luck, and hopefully you've learned an important lesson from this.