Claude review: drm/xe/drm_ras: Add per node cleanup action

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

Patch Review

**Verdict: Correct fix for a real leak, two minor observations.**

This is the most substantial patch. The old code registered a single `xe_drm_ras_unregister_nodes` action in `xe_drm_ras_init()` *after* `register_nodes()` succeeded. If `register_nodes()` failed partway through (e.g., node 0 succeeds but node 1 fails), previously registered nodes were never cleaned up because the batch cleanup action was never registered. The new design registers a `drmm_add_action_or_reset` per node immediately after successful registration, guaranteeing cleanup on unwind.

The error path after the loop is correct:

```c
if (ret) {
    cleanup_node_param(node);
    ras->info[i] = NULL;
}
```

This handles the current (failed) iteration's resources. Previously completed iterations are covered by their already-registered drmm actions.

**Minor observation 1:** If `drmm_add_action_or_reset()` fails, it calls `cleanup_node()` itself (the `_or_reset` semantics), which already runs `cleanup_node_param(node)`. The post-loop `cleanup_node_param(node)` is then a redundant second call. This is **safe** because `cleanup_node_param` sets `device_name = NULL` after freeing, so `kfree(NULL)` on the second call is a no-op. Just worth noting — not a bug.

**Minor observation 2:** `ret` is declared uninitialized:

```c
int i, ret;
```

If `DRM_XE_RAS_ERR_SEV_MAX` were ever 0, `ret` would be used uninitialized in `if (ret)`. In practice this can't happen (there are always correctable and uncorrectable severities), but initializing `ret = 0` would silence potential compiler warnings and be more defensive. Very minor.

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