Removed "label" properties which no longer have any function.
Labels are still used as layer names and as identifiers for sending
behaviors between sides of a split keyboard, so those have been left
alone for now.
* Previous version of multiple overrides of the default value of ZMK_USB
were problematic. Move to using board _defconfig files for the
defaults for those, along with proper `depends on` for ZMK_USB that
accounts for split and split roles.
CONFIG_ZMK_BATTERY_NRF_VDDH and CONFIG_ZMK_BATTERY_VOLTAGE_DIVIDER are
now automatically enabled if a DT node with the matching "compatible"
property is present and enabled, so they no longer need to be manually
set for each board.
battery.c now uses the zmk,battery chosen node to select a battery
sensor. Using the node labeled "BATTERY" is maintained for backwards
compatibility but is now deprecated. Custom boards should switch to
using the chosen node.
# Conflicts:
# app/boards/arm/bluemicro840/bluemicro840_v1.dts
# app/boards/arm/nice60/nice60.dts
# app/boards/arm/nrfmicro/nrfmicro_13.dts
# Conflicts:
# app/boards/arm/bluemicro840/bluemicro840_v1.dts
