Claude review: rust/drm: import ARef from sync crate

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

Patch Review

**Correctness: Good.** On drm-next, `ARef` is defined in `rust/kernel/sync/aref.rs` and is no longer present in or re-exported from `rust/kernel/types.rs`. The current code:

```rust
types::{
    ARef,
    Opaque, //
}, //
```

will indeed fail to compile. The fix changes it to:

```rust
sync::aref::ARef,
types::Opaque, //
```

This matches the convention used elsewhere in the same DRM subsystem — `rust/kernel/drm/driver.rs:14` already imports via `sync::aref::ARef`.

**Minor nit:** The trailing `//` comment on the `types::Opaque` line is a `rustfmt` artifact to force one-import-per-line formatting. That's fine and consistent with the surrounding code style (the existing code had it too). No issue here, just noting it's intentional.

**Commit message:** The commit message is adequate but could be slightly more precise. It says "ARef is defined in sync and is getting used from types causing the build to fail" — it would be clearer to say "ARef was moved from `kernel::types` to `kernel::sync::aref`" to explain *why* the import broke. This is a very minor suggestion and not a blocker.

**No functional concerns.** The change is purely an import path fix with no behavioral impact.

---
Generated by Claude Code Patch Reviewer