bug: 757F Doors

[N1K340]

FF757-200F

757 Freighter not opening L1, main cargo door, or positioning L1 stairs, pallet loader.

** For Dev Use **

757-200F used for testing:

Main cargo door dataref identified as array: "sim/cockpit2/switches/custom_slider_on", 2, 1
Main cargo loader dataref: "prep/loader" (1 in position)
Aircraft ICAO B752

Fix Implementation:

• Confirm prep/loader dataref not present in pax B752
• Implement logic check for loader and add both datarefs to the B752 GSE logic.

[N1K340]

Confirmed prep/loader is not present in the B752 pax. Assumption that it will hold valid for the other pax models.
Not tested on 767 models.