Claude review: drm/exec: Remove the index parameter from drm_exec_for_each_locked_obj[_reverse]

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

Patch Review

**Assessment: Good.**

This hides the loop index variable from callers by introducing helper macros with `__UNIQUE_ID`-generated variable names. The approach is standard kernel practice for preventing name collisions.

The reverse iteration case is correct for `num_objects == 0`:

```c
#define __drm_exec_for_each_locked_object_reverse(exec, obj, __index)	\
	for (unsigned long __index = (exec)->num_objects - 1;		\
	     ((obj) = drm_exec_obj(exec, __index)); --__index)
```

When `num_objects` is 0, `__index` wraps to `ULONG_MAX`, and `drm_exec_obj()` returns NULL immediately. This matches the existing behavior.

All call sites are correctly updated, and the removed `unsigned long index` declarations are the only uses. No issues.

Minor nit: The `unsigned long` type for `__index` in the `for` init is a C99 declaration-in-for, which is fine since the kernel requires C11+.

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Generated by Claude Code Patch Reviewer