Claude review: rust: pci: make Bar lifetime-parameterized

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

Patch Review

Converts `Bar<SIZE>` to `Bar<'a, SIZE>`, storing `&'a Device<Bound>` instead of `ARef<Device>`. The `iomap_region_sized()` method now returns `Result<Bar<'a, SIZE>>` directly instead of `impl PinInit<Devres<Bar<SIZE>>, Error>`.

The notable addition is `Bar::into_devres()`:

```rust
pub fn into_devres(self) -> Result<Devres<Bar<'static, SIZE>>> {
    let bar: Bar<'static, SIZE> = unsafe { core::mem::transmute(self) };
    let pdev = bar.pdev;
    Devres::new(pdev.as_ref(), bar)
}
```

The transmute to `'static` is justified by the Devres invariant: access is revoked on unbind, so the Bar never actually outlives the device. The safety comment is clear.

**Minor observation:** After the transmute, `bar.pdev` is read as a `&'static Device<Bound>`. While this is fine because the Devres owns the Bar and the device outlives the Devres, the code derives `pdev` from the already-transmuted `bar` — this means `pdev` is a `&'static` reference being passed to `Devres::new()`. Since Devres ties the resource to the device and the device *does* outlive the Devres, this should be sound, but worth noting for reviewers.

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