dmaengine: ioatdma: Fix missing kmem_cache_destroy()

Fix missing kmem_cache_destroy() for ioat_sed_cache in
ioat_exit_module().

Noticed via:

```
modprobe ioatdma
rmmod ioatdma
modprobe ioatdma
debugfs: Directory 'ioat_sed_ent' with parent 'slab' already present!
```

Fixes: c0f28ce6

 ("dmaengine: ioatdma: move all the init routines")
Signed-off-by: Nikita Shubin <n.shubin@yadro.com>
Acked-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/20240514-ioatdma_fixes-v1-1-2776a0913254@yadro.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>