Thanks.A nice user at the libreboot irc helped me to find out that that is probably impossible. I did though find out that there was a solution on libreboot.org. It actually says that:
Ocassionally, coreboot changes the name of a given board. If flashrom complains about a board mismatch, but you are sure that you chose the correct ROM image, then run this alternative command:
$ sudo ./flash forceupdate yourrom.rom i.e. forceupdate instead of update did the trick. Thanks for your reply
