drivers/dma: Correct use after free

Move the kfree after the iounmap that refers to the same structure.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@@
expression x,e;
identifier f;
iterator I;
statement S;
@@

*kfree(x);
... when != &x
    when != x = e
    when != I(x,...) S
*x->f
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/dma/coh901318.c

@@ -1294,8 +1294,8 @@ static int __exit coh901318_remove(struct platform_device *pdev)
 	dma_async_device_unregister(&base->dma_slave);
 	coh901318_pool_destroy(&base->pool);
 	free_irq(platform_get_irq(pdev, 0), base);
-	kfree(base);
 	iounmap(base->virtbase);
+	kfree(base);
 	release_mem_region(pdev->resource->start,
 			   resource_size(pdev->resource));
 	return 0;