Claude review: rust: pci: add bus callback sriov_configure(), to control SR-IOV from sysfs

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

Patch Review

The callback plumbing is correct. The `sriov_configure_callback` uses `from_result()` which correctly maps `Result<i32>` to C int (negative for error, non-negative for success).

```rust
+            #[cfg(CONFIG_PCI_IOV)]
+            if T::HAS_SRIOV_CONFIGURE {
+                (*pdrv.get()).sriov_configure = Some(Self::sriov_configure_callback);
+            }
```

The conditional registration using `HAS_SRIOV_CONFIGURE` (from the `#[vtable]` attribute) means `sriov_configure` is only set in the C `pci_driver` when the Rust driver actually implements it. This is important because `pci_iov_disable()` checks `!drv->sriov_configure` to decide whether to call the callback or fall back to `sriov_disable()` directly.

The doc comment example correctly shows usage but the `#[cfg(CONFIG_PCI_IOV)]` on the free function is mildly confusing since the method itself is already cfg-gated on the trait.

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