Fix VFIO discovery and Unconfigure for pre-bound GPUs

[johnahull]

What type of PR is this?

/kind bug

What this PR does / why we need it:

Fixes two bugs in the VFIO passthrough lifecycle:

1. VFIO discovery advertises non-vfio GPUs — enumerateGpuVfioDevices treats any GPU not on the nvidia driver as a VFIO candidate, including GPUs still bound to nvidia. On a system with 2 A40s (one on nvidia, one on vfio-pci), both are advertised as VFIO devices. If the scheduler allocates the nvidia-bound GPU, Configure has to unbind and rebind at runtime, which can hang on NVLink systems. The fix adds a getDriver() check — only GPUs actually bound to vfio-pci are advertised.

2. Unconfigure rebinds pre-bound GPUs — When a GPU was already on vfio-pci before Configure ran (pre-bound at boot), Unconfigure tries to rebind it to nvidia, which hangs indefinitely on NVLink systems during fabric reconfiguration. The fix tracks the pre-Configure driver binding and skips the rebind if the GPU was already on vfio-pci.

Changes from v1:

Reworked based on @varunrsekar's feedback:

• Dropped /dev/vfio/vfio CDI change — use DeviceClass config with enableAPIDevice: true instead
• Dropped sysfs fallback for vfio_pci/IOMMU checks — helm chart deployment mounts /host-root correctly
• Dropped vfio-pci.ids kernel cmdline detection — will file as separate feature request
• Kept VFIO discovery driver filter (issue 2) and preConfigureDriver tracking (issue 3)

How to verify it:

On a multi-GPU system with some GPUs on nvidia and some on vfio-pci:

• Before fix: all GPUs appear as gpu-vfio-* in ResourceSlice regardless of driver binding
• After fix: only GPUs bound to vfio-pci appear as gpu-vfio-*

Which issue(s) this PR fixes:

Fixes #1089 (issues 2 and 3)

Fix VFIO device discovery to only advertise GPUs bound to vfio-pci, and skip Unconfigure rebind for pre-bound GPUs.

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: johnahull
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