Claude review: rust: pci: add {enable,disable}_sriov(), to control SR-IOV capability

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

Setting `managed_sriov = true` unconditionally for all Rust PCI drivers is the right call. For non-SR-IOV devices, `pci_iov_disable()` returns immediately on `!dev->is_physfn`, so there's no overhead.

The methods are correctly placed on `Device<device::Core>` and gated with `#[cfg(CONFIG_PCI_IOV)]`.

```rust
+    pub fn enable_sriov(&self, nr_virtfn: i32) -> Result {
```

**Minor**: `nr_virtfn` as `i32` matches the C API, but semantically VF counts are non-negative. A `u16` would be more idiomatic since SR-IOV is limited to 16 bits in the PCIe spec. However, matching the C signature avoids conversion overhead and is consistent with the rest of the Rust PCI bindings.

---
Generated by Claude Code Patch Reviewer