[split] U-Boot with NVMe support, keyboard & display working

[Arwen]

Actually, I'd put the builtin USB keyboard at a higher priority than the eDP.

With USB keyboard support, (builtin and or external), we can setup a sequence of events at boot:

• Pause & blink LED, (which one?), for a short time, (5 seconds?). Perhaps power LED, alternating red & green.
  
• During this time, accept keyboard input
  
• Select boot device of:
  
  1. USB
     
  2. MicroSD card
     
  3. NVMe
     
  4. eMMC
     

With this, we can leave an SD card installed, and over-ride booting to it.

Or even allow re-arranging the default boot order to be fastest first, since we can select something else if needed.

1. NVMe
   
2. eMMC
   
3. MicroSD card
   
4. USB