samples: nrf: mesh: onoff-app: Convert to the new GPIO API
samples: nrf: mesh: onoff-app: Convert to the new GPIO API

Covert to the new GPIO API, using logical levels instead of raw ones.

Signed-off-by: Carles Cufi <853081dc8dca4fe6a7e3c984752718b5db36e060@nordicsemi.no>

Vudentz/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,nashif/zephyr,Vudentz/zephyr,Vudentz/zephyr,Vudentz/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,nashif/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,nashif/zephyr,nashif/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,Vudentz/zephyr