Extend available EEPROM driver config

[zvecr]

Description

Currently adds:

    "eeprom": {
        "driver": "i2c",
        "i2c": {
            "device": "24lc256",
            "address": "0xA8",
            "write_protect_pin": "B5"
        }
    },

    "eeprom": {
        "driver": "spi",
        "spi": {
            "device": "mb85rs64v",
            "chip_select_pin": "B5"
        }
    },

Where eeprom.*.device generates EEPROM_<driver>_<device>.

// TODO:
      8 EXTERNAL_EEPROM_SPI_CLOCK_DIVISOR
      4 EEPROM_SIZE
      1 EXTERNAL_EEPROM_PAGE_SIZE
      1 EXTERNAL_EEPROM_BYTE_COUNT
      1 EXTERNAL_EEPROM_ADDRESS_SIZE

Will add docs when structure is finalised.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).