Claude review: drm: Drop unused drm_device_class_(un)register API

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

Patch Review

**Correctness: Good.**

- The removal of `drm_class_device_register()` and `drm_class_device_unregister()` from `drm_sysfs.c` is complete — both function bodies and their `EXPORT_SYMBOL_GPL` lines are removed.
- The header `drm_sysfs.h` correctly removes both function declarations and the `struct device` forward declaration, which was only needed for those function prototypes.
- The remaining declarations in `drm_sysfs.h` (`drm_sysfs_hotplug_event`, `drm_sysfs_connector_hotplug_event`, `drm_sysfs_connector_property_event`) use `struct drm_device`, `struct drm_connector`, and `struct drm_property` — none require `struct device`, so removing that forward declaration is safe.

**Nit (commit message):** The subject says `drm_device_class_(un)register` but the actual function names are `drm_class_device_register` / `drm_class_device_unregister` — the word order is swapped. This is a minor cosmetic issue in the subject line:

```
Subject: [PATCH] drm: Drop unused drm_device_class_(un)register API
```

Should be:

```
Subject: [PATCH] drm: Drop unused drm_class_device_(un)register API
```

**No other issues.** The patch is minimal, correct, and safe to merge (with optionally fixing the subject typo).

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