Support for Orin NX

[danielfullmer]

Description of changes

This PR adds support for the Orin NX, running on the Xavier NX devkit.

There are two known issues:

1. Flashing a factory Orin NX works the first time, but fails the second time: Flashing Orin NX fails the second time #33
2. It currently requires the USB_OTG kernel config option to be disabled, or else the kernel crashes at boot: Orin NX kernel panic with USB OTG enabled #34

Testing

Flashed and booted NixOS on an Orin NX

[danielfullmer]

Merging this PR even though there are two serious known issues. We'll resolve them in future PRs when we figure out a solution. Orin NX in jetpack-nixos should be considered experimental until we have these fixed.