Claude review: drm/i915/display: Error codes for async flip failures

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

Patch Review

**Issues:**

```c
	if (intel_crtc_needs_modeset(new_crtc_state)) {
-		drm_dbg_kms(display->drm,
-			    "[CRTC:%d:%s] modeset required\n",
-			    crtc->base.base.id, crtc->base.name);
+		drm_mode_atomic_add_error_msg(&state->base.error_code,
+					      DRM_MODE_ATOMIC_CRTC_NEED_FULL_MODESET,
+					      "[CRTC:%d:%s] requires full modeset",
+					      crtc->base.base.id, crtc->base.name);
```
- **Inconsistent Logging**: Original used `drm_dbg_kms`, now uses `drm_dbg_atomic` (inside add_error_msg). This changes which debug category the message appears in.
- **Message Change**: "modeset required" vs "requires full modeset" - why change?

```c
+			drm_mode_atomic_add_error_msg(&state->base.error_code,
+						      DRM_MODE_ATOMIC_INVALID_API_USAGE,
+						      "[PLANE:%d:%s] pixel format %p4cc / 0x%llx modifier does not support async flip",
```
- **Format String**: Reordering format string from `%p4cc / modifier 0x%llx` to `%p4cc / 0x%llx modifier` is unnecessary and makes it harder to review.
- **Message Truncation Risk**: This is a long message that may be truncated to 128 chars.

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