Claude review: gpu: ipu-v3: clean up kernel-doc warnings

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

Patch Review

**Correctness: All changes are correct.**

1. **`/* private: */` for `list`** (line 30-31 in patched file):
   ```c
   /* private: */
   /* internal to image converter, callers don't touch */
   struct list_head list;
   ```
   Properly marks `list` as a private member, suppressing the "struct member 'list' not described" warning. The existing comment already indicated this was internal — the `/* private: */` tag makes kernel-doc aware of that intent.

2. **`typedef` prefix fix** (line 36):
   ```c
   * typedef ipu_image_convert_cb_t - conversion callback function prototype
   ```
   Previously `ipu_image_convert_cb_t` without the `typedef` keyword, which confused kernel-doc into parsing it as a function prototype (the "expecting prototype for ipu_image_convert_cb_t(). Prototype was for void() instead" warning). This is the correct kernel-doc syntax for typedefs.

3. **`Returns` -> `Returns:` changes** (lines 64, 83, 127, 162): All four use the standard kernel-doc `Returns:` tag with the colon, which is required for kernel-doc to recognize return value documentation.

4. **Paragraph reordering in `ipu_image_convert_prepare()`** (lines 81-85): The "In V4L2, drivers should call..." sentence was moved above the `Returns:` block. This is correct — kernel-doc expects `Returns:` to be the last section in a function doc comment, as content after it is treated as part of the return description.

5. **Added `Returns:` for `ipu_image_convert_queue()`** (line 127):
   ```c
   * Returns: 0 on success or -errno on error.
   ```
   Clear and appropriate for an `int`-returning function.

6. **Added `Returns:` for `ipu_image_convert()`** (lines 162-163):
   ```c
   * Returns: pointer to the created &struct ipu_image_convert_run that has
   * been queued on success; an ERR_PTR(errno) on error.
   ```
   Uses the `&struct` cross-reference syntax correctly.

**Minor pre-existing nit (not introduced by this patch):** Line 85 and line 157 both contain the typo "retrictions" (should be "restrictions"). This predates the patch and is out of scope, but Randy may want to fix it in a follow-up.

**Verdict: No issues. Patch is ready to merge.**

---
Generated by Claude Code Patch Reviewer