net: openthread: fix `otPlatRadioSetMacKey` when asserts are disabled
net: openthread: fix `otPlatRadioSetMacKey` when asserts are disabled

Ensure `otPlatRadioSetMacKey` is properly implemented when asserts are
disabled.

Signed-off-by: Eduardo Montoya <c6d924925ebf82d772472f7877e771cedf439387@nordicsemi.no>

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