HARD FAULT : Add sanity check to sx126x driver when handling retention list

[MarekNovakACRIOS]

The same as described here applies: https://github.com/Lora-net/SWL2001/pull/72 In one sentence - without the sanity check, reading ouf of bounds of an array placed on stack can happen -> this will cause reading outside of RAM/SRAM region, due to stack being placed at the end of SRAM/RAM region -> this will generate a hardfault or a memfault or take down the system...