Implement cbfs for passing information to SeaBIOS

[FlyGoat]

Implement CBFS to pass sideband information to SeaBIOS, to avoid being too intrusive to SeaBIOScode.

Since we are already using coreboot tables to pass framebuffer information, we just need to pick:

https://mail.coreboot.org/hyperkitty/list/[email protected]/thread/PSLZAMCG7C5IU6TLEGXWZCESXHPYUS76/

and copy cbfs stuff from coreboot.