Claude review: rust: gpuvm: add GpuVa struct

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

Patch Review

Introduces `GpuVa<T>`, `GpuVaAlloc<T>`, and `GpuVaRemoved<T>`.

**SAFETY comment typo in `obj()`:**
```rust
/// Returns the GEM object.
pub fn obj(&self) -> &T::Object {
    // SAFETY: The `gem.offset` field of `drm_gpuva` is immutable.
    unsafe { <T::Object as IntoGEMObject>::from_raw((*self.as_raw()).gem.obj) }
}
```
The SAFETY comment says "gem.offset" but it's accessing `gem.obj`. Should say "gem.obj".

**`GpuVaAlloc::prepare` consumes self but leaks memory on panic:**
```rust
pub(super) fn prepare(mut self, va_data: impl PinInit<T::VaData>) -> *mut bindings::drm_gpuva {
    let va_ptr = MaybeUninit::as_mut_ptr(&mut self.0);
    let Ok(()) = unsafe { va_data.__pinned_init(&raw mut (*va_ptr).data) };
    KBox::into_raw(self.0).cast()
}
```
The `let Ok(()) =` pattern on an infallible init is fine. But `self` is consumed by move, and `KBox::into_raw` forgets the box — the caller takes ownership of the raw pointer. This is correct for the intended usage where the pointer is passed to `drm_gpuva_map`/`drm_gpuva_remap`.

**Missing `GpuVaAlloc` destructor:** If a `GpuVaAlloc` is dropped (e.g., the `unused_va` in `OpRemapRet`), the `KBox<MaybeUninit<GpuVa<T>>>` is dropped which frees the allocation. However, since `MaybeUninit` doesn't run destructors and the memory was zeroed (not initialized), this is actually correct — no `T::VaData` destructor runs because none was initialized. Good.

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Generated by Claude Code Patch Reviewer