Verify offboard mode for rover

[SalimTerryLi]

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Describe problem solved by the proposed feature
This TODO prevents the offboard mode working on a rover. The expected solution should not limit the offboard mode as multirotor-only.

Describe your preferred solution
I' m asking for adding att_sp.thrust_body[0] = set_attitude_target.thrust; below but I don' t know how it would affect other frame types.
This will fix that rover cannot get throttle value from attitude setpoints.

Describe possible alternatives
I don' t know if there is any other way to solve this.

[julianoes]

@SalimTerryLi thanks for raising this! Have you already tried to make this work by changing it? If so you could make a pull request that we could discuss.

[julianoes]

FYI @ItsTimmy

[Jaeyoung-Lim]

It would be awesome if this fix leads to enabling offboard mode in fixed wing too

[SalimTerryLi]

#12149