Setting gpio.poweroff is not idempotent

See <https://github.com/ftCommunity/tx-pi/blob/32b9a37adcf31cd1b44ca6cf251f8ac0aaf87187/setup/tx-pi-setup.sh#L236>

echo "dtoverlay=gpio-poweroff,gpiopin=4,active_low=1" >> /boot/firmware/config.txt

If the script is run more than one time the overlay is added again. Not a big problem though.