The "BIOS" in this board is U-Boot. The order in which devices are searched for bootable kernels seems to be controlled by a set of commands and variables stored as part of U-Boot's environment on the SPI nor-flash.
So, you will need to speak with U-Boot. Hook up a USB-to-3.3-volt-serial adapter to the correct three GPIO pins and access it via Kermit or minicom or some other such terminal emulator. Power on the LaFrite. You should see a bunch of messages from U-Boot. As soon as you do, hit the Escape key... this will interrupt the boot process and give you a command prompt. You will want to use commands such as help, printenv, setenv, and saveenv to change the variables that affect the boot ordering. The whole U-Boot manual is online... web-search for it.
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So, you will need to speak with U-Boot. Hook up a USB-to-3.3-volt-serial adapter to the correct three GPIO pins and access it via Kermit or minicom or some other such terminal emulator. Power on the LaFrite. You should see a bunch of messages from U-Boot. As soon as you do, hit the Escape key... this will interrupt the boot process and give you a command prompt. You will want to use commands such as help, printenv, setenv, and saveenv to change the variables that affect the boot ordering. The whole U-Boot manual is online... web-search for it.