RC_Channel: rename rc option to AHRS AutoTrim

Author: rmackay9

libraries/RC_Channel/RC_Channel.cpp

@@ -245,7 +245,7 @@ const AP_Param::GroupInfo RC_Channel::var_info[] = {
     // @Values{Plane}: 179:ICEngine start / stop
     // @Values{Copter, Plane}: 180:Test autotuned gains after tune is complete
     // @Values{Plane}: 181: QuickTune
-    // @Values{Copter}: 182: In flight AHRS trim adjust
+    // @Values{Copter}: 182: AHRS AutoTrim
     // @Values{Plane}: 183: AUTOLAND mode
     // @Values{Rover}: 201:Roll
     // @Values{Rover}: 202:Pitch