Merge branch '2021-08-30-kconfig-migrations-part1' into next

- Begin merging some Kconfig migration, and CONFIG namespace cleanup
  series in.  This gives us:
  - A number of I2C symbols migrated over
  - DWC2, i8042, altera_spi and a few other areas updated to use CFG not
    CONFIG for the concept of "configuration space" defines.
  - Rename CONFIG_EXTRA_ENV_BOARD_SETTINGS to EXTRA_ENV_BOARD_SETTINGS
  - Some dead code removal.
  - Rename a number of CONFIG symbols that were only referenced within
    the config header to not use CONFIG as a prefix.