Orin AGX 64gb fab from "000" to "300"

[TanelDettenborn]

Description of changes

Jetson 35.6 BSP "jetson_board_spec.cfg"-file uses/defines Orin AGX 64gb "300" as a fab value.

Testing

Evaluates and compiles.

[danielfullmer]

Thanks for the catch. It looks like this changed upstream between Jetpack 5.1.1 and Jetpack 5.1.2 in the jetson_board_spec.cfg file. Since the TegraCompatSpec variable doesn't include the FAB for Orin AGX (see ota_helpers.func), and there doesn't appear to be any flash script behavior conditional on FAB for Orin AGX, I think this shouldn't have any functional difference. Still good to merge to keep in sync with Jetpack.