[LoRaWAN] Move TX power logic to function

[StevenCellist]

Some applications might want to alter the Tx power, e.g. for testing LoRaWAN network coverage. Also, this moves the setOutputPower logic to one single function for better readability.

[jgromes]

Thanks, this looks good. Just one point, would it be possible to change the method name to setOutputPower? That's used for the transceivers as well.

[StevenCellist]

Understandable, but within the LoRaWAN scheme it's specified as Tx Power and would prevent some mistakes between function calls.
But completely your call, it's not much of a difference. Let me know :)

[jgromes]

Hmm, that's actually a good point - event the transmit/receive methods are called uplink and downlink, so let's keep the current name. Though in that case, setTxPower is missing from keywords (keep in mind the files uses true tabs, not spaces).

[StevenCellist]

Ah, that was the problem.. got it and done

[jgromes]

Perfect, thank you very much!

BTW the only reason I have not yet released a new update with your LoRaWAN changes is that the STM32 framework for Arduino is broken for the STM32WL series. There should be an update coming soon.