* Set default revision to 5.20
* update mikoto board defs
* add revision info to mikoto.zmk.yml
* use zephyr aliases to handle mikoto_520
* enable pull-ups for on-board i2c
* Move away from DT_LABEL.
* Move to DEVICE_DT_GET for non-behavior device access.
* Move various drivers to `gpio_spec_dt` and `DT` related macros.
* Remove mcp23017 while at it, since better upstream driver is
available.