Modem does not respond to `+RFPOWER=`

[flhofer]

Tested with 1.2.0 and 1.2.3
Sending +RFPOWER= 0, 4 gives no response and the library goes in timeout returning an error. Tried to extend the timeout to 10 seconds, no change.

Tested using MKRWAN library 1.10 with DEBUG

[flhofer]

Seems the same happens with +RSSI

[flhofer]

Fixed here. Missing +OK= prints in FW
flhofer@d246fb1

[flhofer]

See #35