UEFI: Update Boot Device Entry corrupts config

On recent versions of UEFI, with the "local FDT" modifications, using the Boot Menu "[2] Update Boot Device Entry" can sometime corrupt the config, meaning that NOR flash has to be erased before you can configure the board again.

To erase the NOR flash, you follow these steps:

1) mount the USBMS
2) edit /media/xxxxx/config.txt
change AUTORUN to be FALSE
3) unmount USBMS
4) reboot the board
5) you'll end up at the Boot Loader command prompt "Cmd> "
6) enter the command "flash", the command prompt will change to "Flash> "
7) enter the command "eraseall", this will erase the whole of NOR flash.
8) when it completes, after 10 or 15 mins, I think, maybe longer,
enter the command "exit"
9) then enter the command "usb_on"
10) mount the USBMS
11) restore config.txt
12) unmount USBMS
13) enter the command "reboot" on the board