CVE-2026-53325 agp/amd64: Fix broken error propagation in agp_amd64_probe()

In the Linux kernel, the following vulnerability has been resolved: agp/amd64: Fix broken error propagation in agpamd64probe A NULL pointer dereference was observed in the AMD64 AGP driver when running in a virtualized environment e.g. qemu/kvm without a physical AMD northbridge. The crash occurs...