You would probably need to back port the ethernet driver from 4.17 to 4.9 (not easy, but easier than porting all of 4.9 to 4.17). Device tree would not be altered for anything “hot plug”, e.g., PCI or USB.
“lspci” is already active. If lspci can see a device, then the device will list regardless of whether the device has a driver to function with or not. Usually if lspci fails it means the signal quality is too low to see the device, or perhaps the device has a power deliver issue. In the case of FPGAs they do not respond until booted, and lspci won’t show such a device unless PCIe enumeration is delayed.
On a desktop PC there is usually an ability to late detect a device appearing on the PCIe bus. The meaning is that if a slow responding device (such as an FPGA still booting) does not respond at initial power on, then the PC would still detect the device after the system and device are both booted. Jetsons require power savings be considered, and if initial power up does not detect a device, then PCIe is left unpowered. This case implies not even the PCIe bridge will be listed…it isn’t on.
Ethernet cards do not require late enumeration. So I would suspect that power delivery is inadequate, or that there is some signal quality issue.