drivers/sensor: iis2iclx: clean unused leftovers
drivers/sensor: iis2iclx: clean unused leftovers

Remove few unused declarations.

Signed-off-by: Armando Visconti <d93ca24ded08d03c3aa60af6d2fd0eb7ce54da11@st.com>

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