pm: device_runtime: fix unused parameter warning
pm: device_runtime: fix unused parameter warning

When using `-Wunused-parameter`, compiler complains about
unused parameter.

Signed-off-by: Cyril Fougeray <777c84ff5a447bf540d7d588bb28ce156dfaa082@worldcoin.org>

zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr