fix Victron Orion TR device description

[benderl]

Description:

This PR fixes the device description of the Victron Orion TR, introduced in #708 .

• Remove data points "current_in" and "current_out". This are leftovers from copy/paste of Orion-XS definition.
• Added data point "off_reason".
• Fixed condition and unsigned format of "volt_in".
• Adjusted test case.
• Cleanup doc file.

Checklist:

• The pull request is done against the latest development branch
• Only one feature/fix was added per PR and the code change compiles without warnings
• I accept the DCO.

[DigiH]

Thanks