Claude review: backlight: apple_bl: Convert to a platform driver

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

Patch Review

**Overall**: This is a correct and straightforward ACPI-to-platform driver conversion. No functional issues found.

**Positive observations:**

1. The `#include <linux/platform_device.h>` addition is correctly placed in alphabetical order.

2. The function signatures are updated correctly:
   - `apple_bl_add(struct acpi_device *dev)` → `apple_bl_probe(struct platform_device *pdev)` — the rename from `add` to `probe` follows platform driver convention.
   - `apple_bl_remove(struct acpi_device *dev)` → `apple_bl_remove(struct platform_device *pdev)` — the `void` return type matches `platform_driver.remove` (line 241 of `platform_device.h`).

3. The driver struct conversion is correct:
   ```c
   static struct platform_driver apple_bl_driver = {
       .probe = apple_bl_probe,
       .remove = apple_bl_remove,
       .driver = {
           .name = "Apple backlight",
           .acpi_match_table = apple_bl_ids,
       },
   };
   ```
   The `acpi_match_table` correctly replaces the old `.ids` field, keeping the same `apple_bl_ids` array.

4. The init/exit functions correctly switch from `acpi_bus_register_driver`/`acpi_bus_unregister_driver` to `platform_driver_register`/`platform_driver_unregister`.

**Minor observation (not a bug):**

- Neither the old `acpi_device *dev` parameter nor the new `platform_device *pdev` parameter is actually used inside `apple_bl_probe()` or `apple_bl_remove()`. The driver relies entirely on global state (`hw_data`, `apple_backlight_device`). This is a pre-existing pattern and not something introduced by this patch, so it's fine to leave it as-is. However, a follow-up could pass `&pdev->dev` to `backlight_device_register()` instead of `NULL` (line 182-183), which would create a proper device hierarchy in sysfs. This is purely optional.

- The `MODULE_DEVICE_TABLE(acpi, apple_bl_ids)` at line 242 is correctly retained, ensuring module autoloading still works.

**Reviewed-by worthy**: Yes, this patch is correct and ready.

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