pymesh: do not (re-)create LoRa instances in pymesh_config

[peter-pycom]

It seems there is a rare chance to end up with a frozen device at the point where the lora=LoRa() object is recreated. There is no real need to do this inside pymesh_config, so as a workaround we simply make one object only and pass the lora_mac

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}