Add option to set tx power >20 for sx1262 modules

Sx1262 LoRa modules theoretically support power outputs up to +22dBm but freakwan will not set values >20 dBm (max power supported by sx1276 I believe).
Should we check whether the freakwan device has a sx1262 or sx1276 through config before sending the message about invalid power (and set it accordingly if valid)?

I am referring for example to this line `send_reply("-Invalid tx power (dbm). Use 2-20.")` in `clictrl.py` which invalidates settings higer than 20dBm (which sx1262 modules support)