No Longer maintained Please use GnuBee_PCx_uboot
Forked from pinney/MT7621-u-boot-mod @ commit 5688587b9031073d95c8af5e878cf6ce8f3c0962
Flashing the bootloader is risky.
If you like expensive bricks proceed without caution.
You will need a working Serial Console and a TFTP server.
From the Serial Console (UART) : Option 9