ion: Fix iommu rewrite additions

These pointers weren't converted in the iommu rewrite commit, causing
undefined behavior (and out-of-bounds memory access). Fix them.

Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>
Signed-off-by: Adam W. Willis <return.of.octobot@gmail.com>

drivers/staging/android/ion/ion.c

@@ -245,7 +245,8 @@ static struct sg_table *ion_map_dma_buf(struct dma_buf_attachment *attachment,
 	struct ion_dma_buf_attachment *a = attachment->priv;
 	struct sg_table *table;
 	int count, map_attrs;
-	struct ion_buffer *buffer = attachment->dmabuf->priv;
+	struct ion_buffer *buffer = container_of(attachment->dmabuf->priv,
+						 typeof(*buffer), iommu_data);
 
 	table = a->table;
 
@@ -276,7 +277,8 @@ static void ion_unmap_dma_buf(struct dma_buf_attachment *attachment,
 			      enum dma_data_direction direction)
 {
 	int map_attrs;
-	struct ion_buffer *buffer = attachment->dmabuf->priv;
+	struct ion_buffer *buffer = container_of(attachment->dmabuf->priv,
+						 typeof(*buffer), iommu_data);
 	struct ion_dma_buf_attachment *a = attachment->priv;
 
 	map_attrs = attachment->dma_map_attrs;