iommu/vt-d: Constify intel_dma_ops

Most dma_map_ops structures are never modified. Constify these
structures such that these can be write-protected.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 0ca985b..1a79a4e 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3954,7 +3954,7 @@
 	return !dma_addr;
 }
 
-struct dma_map_ops intel_dma_ops = {
+const struct dma_map_ops intel_dma_ops = {
 	.alloc = intel_alloc_coherent,
 	.free = intel_free_coherent,
 	.map_sg = intel_map_sg,