Add comment about use in interrupt context to Rs485's destructor
Add comment about use in interrupt context to Rs485's destructor

No CHECK_FUNCTION_CONTEXT() is necessary here, as it's already present
in destructor of base class - SerialPort.
jasmin-j/distortos,DISTORTEC/distortos,CezaryGapinski/distortos,CezaryGapinski/distortos,CezaryGapinski/distortos,CezaryGapinski/distortos,jasmin-j/distortos,jasmin-j/distortos,DISTORTEC/distortos,jasmin-j/distortos,CezaryGapinski/distortos,DISTORTEC/distortos,DISTORTEC/distortos,jasmin-j/distortos