vulkan/cmd_queue: Constify vk_cmd_queue.alloc

The implementation shouldn't modify the allocator.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Jason Ekstrand <jason.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15311>

src/vulkan/util/vk_cmd_queue_gen.py

@@ -59,7 +59,7 @@ extern "C" {
 #endif
 
 struct vk_cmd_queue {
-   VkAllocationCallbacks *alloc;
+   const VkAllocationCallbacks *alloc;
    struct list_head cmds;
 };