Update lora_radio_helper.h for STM32WL_LoRaRadio

[jeromecoutant]

Hi

STM32WL_LoRaRadio class has been updated in ARMmbed/mbed-os#14734

@hallard

[elrom]

With this fix It compiles - but AFAICT it doesn't actually work. I haven't had a chance to debug it though.

[jeromecoutant]

It's working with my test gateway:

 Mbed LoRaWANStack initialized

 CONFIRMED message retries : 3

 Adaptive data  rate (ADR) - Enabled

 Connection - In Progress ...

 Connection - Successful

 Dummy Sensor Value = 3

 23 bytes scheduled for transmission

 Message Sent to Network Server

 Dummy Sensor Value = 5

 23 bytes scheduled for transmission

 Message Sent to Network Server

 Dummy Sensor Value = 7

 23 bytes scheduled for transmission

 Message Sent to Network Server

 Dummy Sensor Value = 9

 23 bytes scheduled for transmission

 Received message from Network Server
 RX Data on port 15 (26 bytes): 44 75 6d 6d 79 20 53 65 6e 73 6f 72 20 56 61 6c 75 65 20 69 73 20 31 30 38 37