iommu: Make of_device_id array const

Make of_device_id array const, because all OF functions handle it as const.

Signed-off-by: Kiran Padwal <kiran.padwal@smartplayin.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
diff --git a/drivers/iommu/omap-iommu.c b/drivers/iommu/omap-iommu.c
index e202b0c..47517cf 100644
--- a/drivers/iommu/omap-iommu.c
+++ b/drivers/iommu/omap-iommu.c
@@ -1006,7 +1006,7 @@
 	return 0;
 }
 
-static struct of_device_id omap_iommu_of_match[] = {
+static const struct of_device_id omap_iommu_of_match[] = {
 	{ .compatible = "ti,omap2-iommu" },
 	{ .compatible = "ti,omap4-iommu" },
 	{ .compatible = "ti,dra7-iommu"	},