Claude review: dma-mapping: avoid random addr value print out on error path

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

Patch Review

**Subject**: `dma-mapping: avoid random addr value print out on error path`  
**Files Modified**: `kernel/dma/direct.h`  
**Verdict**: ✅ **Acceptable** (with minor concern)

#### Technical Review

The patch fixes a legitimate bug where `dma_addr` is uninitialized when both conditions are true:
- `is_swiotlb_force_bounce(dev)` returns true
- `DMA_ATTR_MMIO` is set in attrs

**Code Analysis** (kernel/dma/direct.h:118-120):
```c
if (is_swiotlb_force_bounce(dev)) {
    if (attrs & DMA_ATTR_MMIO)
-       goto err_overflow;
+       return DMA_MAPPING_ERROR;
```

**Correctness**:
- ✅ Eliminates uninitialized variable usage
- ✅ Semantically correct - returning `DMA_MAPPING_ERROR` is appropriate for this error condition
- ✅ Fixes tag references commit e53d29f957b3

**Concerns**:
- ⚠️ **Code duplication**: Now returns `DMA_MAPPING_ERROR` in multiple places. The `err_overflow` label still exists and is used later.
- ⚠️ **Silent behavioral change**: The `err_overflow` label prints a warning with `dma_addr`. By skipping it, we lose the warning message entirely (though it was printing garbage). Should consider whether a warning is still useful here.

**Question**: Is losing the warning message intentional? The `err_overflow` path calls:
```c
dev_err_once(dev, "overflow %pad+%zu of DMA mask %llx bus limit %llx\n",
             &phys, size, (u64)dma_get_mask(dev), dev->dma_range_map->...);
```

This could be valuable diagnostic information even without the dma_addr.

**Minor**: Commit message has typo: "unitialized" should be "uninitialized"

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