lora: sx1276: Add missing RtcTick2Ms function definition
lora: sx1276: Add missing RtcTick2Ms function definition

RtcTick2Ms function is required for upcoming LoRaWAN support. Hence,
add definition for it.

Signed-off-by: Manivannan Sadhasivam <c29222e98de6437a383e8d946a9b202298e0aa3a@kernel.org>

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