Claude review: drm/msm: Fix iommu_map_sgtable() return value check and avoid WARN

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

Patch Review

**Status: Good**

This patch makes two changes: fixes the type from `size_t` to `ssize_t`, and replaces the `WARN_ON(!ret)` with a proper error return:

```c
-	size_t ret;
+	ssize_t ret;
...
 	ret = iommu_map_sgtable(iommu->domain, iova, sgt, prot);
-	WARN_ON(!ret);
+	if (ret < 0)
+		return ret;
 
 	return (ret == len) ? 0 : -EINVAL;
```

The function `msm_iommu_map` returns `int`, and `ret` is `ssize_t`. On the error path, `return ret` narrows `ssize_t` to `int`, which is safe for negative errnos. On the success path, the existing `(ret == len) ? 0 : -EINVAL` check is preserved, correctly detecting partial mappings.

The removal of `WARN_ON` is an improvement -- a WARN splat in dmesg for a mapping failure that the caller can handle is too noisy. Returning the error code lets the caller decide how to handle it.

No issues.

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Generated by Claude Code Patch Reviewer