Bug#1006774: bug seems to depend on motherboard/CPU type

[Luc Maisonobe]

The bug is still present in grub 2.06-13.
It however seems to happen only with some motherboard/CPU
configurations.
Here are 3 different configurations I had to test recently:

  - motherboard MSI X570-A PRO, CPU AMD Ryzen 5 3600
         bug occurs: boot freezes as soon as one key is pressed
                     on a USB keyboard due to repeated key, only
                     way to select menu is to use an old keyboard
  - motherboard ASrock Q87M vPro, CPU Intel core I7 5820K
         no bug: can select boot menu entries from USB keyboard
  - motherboard ASUS H170 pro gaming, CPU Intel core I7-6700
         no bug: cas select boot menu entries from USB keyboard

Every other components in the PC were exactly the same: I just mounted
the motherboard/CPU in the same box at a few days interval

Luc