parseGPUWithSupplementalDocs did not read PCIeInterface from the device
doc, only from function docs. xFusion GPU PCIeCard entries carry link
width/speed in PCIeInterface (LanesInUse/Maxlanes/PCIeType/MaxPCIeType)
so GPU link width was always empty for xFusion servers.
Also apply the xFusion OEM function-level fallback for GPU function docs,
consistent with the NIC and PCIeDevice paths.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>