Joystick button assignement

#### Issue details
Joystick button assignement are not saved with Auto-detect

Pitch and Throttle are inverted and are not corresponding to the mapping made in the RCMAP parameters.

#### Version
Mission planner 1.3.41.8

#### Platform
[X] All
[ ] AntennaTracker
[ ] Copter
[ ] Plane
[X] Rover

#### Airframe type
_What type of airframe (flying wing, glider, hex, Y6, octa etc)_

#### Hardware type
Rover - Navio 2

#### Logs
_Please provide a link to any relevant logs that show the issue_

Start by reproducing the issue in Mission Planner 1.3.41.8 with the Rover/Navio 2 setup, checking joystick assignments under Auto-detect and the RCMAP parameters. Done means assignments are saved and Pitch and Throttle correspond to the configured mapping.

Written by the indexing model from the issue text.