tools/eeprom: Add vim modelines
tools/eeprom: Document that it needs python3
docs/EEPROM: Specify SPI speed and power usage fields

Additionally, add a small python script that generates a full table of
possible values in rst format.
tools/eeprom: Include SPI speed and power usage

This adds support for the minifloat formats used and automatically
encodes the value given. Since rounding errors may occur, and since
these could be significant, all rounded values are printed afterwards as
well.