Claude review: dma-buf: heaps: use max3 in dma_heap_ioctl

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

Patch Review

**Status: Clean**

The patch does two things:

1. Adds `#include <linux/minmax.h>` (line 16 after patch), which provides the `max3` macro. This is correctly placed in alphabetical order among the existing includes.

2. Replaces the nested `max()` calls:
```c
-	ksize = max(max(in_size, out_size), drv_size);
+	ksize = max3(in_size, out_size, drv_size);
```

All three variables are declared as `unsigned int` at line 138:
```c
unsigned int in_size, out_size, drv_size, ksize;
```

This makes the `max3` call type-safe with no risk of signed/unsigned comparison issues.

The change is functionally equivalent and slightly more readable. No concerns.

**Reviewed-by: Already has R-b from T.J. Mercier.**

---
Generated by Claude Code Patch Reviewer