Keyboard reset code needs to be more resilient

[roscopeco]

The keyboard init in the firmware needs to actively reset the keyboard. Currently it can get confused (and fail detection) if:

• The keyboard has been left in scan mode
• The keyboard has sent mouse packets that have not been completely processed

We should make sure we empty the buffers, send a bunch of NOPs, and then actively set ASCII mode and sensible defaults in the firmware init code.