gpu: ion: Add missing iommu heap destroy call

When a heap is destroyed a heap type specific
function is called to release memory that the heap
structures used. A case statement handling destroying
the iommu heap is missing. Add missing case statement.

Change-Id: I1aa54209a55db06becc570f65ecf0f740d2e9545
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
diff --git a/drivers/gpu/ion/ion_heap.c b/drivers/gpu/ion/ion_heap.c
index bfa20d0..6ea49db 100644
--- a/drivers/gpu/ion/ion_heap.c
+++ b/drivers/gpu/ion/ion_heap.c
@@ -72,6 +72,9 @@
 	case ION_HEAP_TYPE_CARVEOUT:
 		ion_carveout_heap_destroy(heap);
 		break;
+	case ION_HEAP_TYPE_IOMMU:
+		ion_iommu_heap_destroy(heap);
+		break;
 	case ION_HEAP_TYPE_CP:
 		ion_cp_heap_destroy(heap);
 		break;