Do Not Use txtmode Rom When Flashing Libreboot

When flashing Libreboot, please choose a corebootfb rom, it was shipped with complete libgfxinit support.

Unless you know & understand what you are doing, DO NOT use an txtmode rom. This rom will cause graphic rendering issue when booting. You will even encounter issues when booting GRUB with graphical interface or installing Trisquel GNU/Linux.