[SPARC64]: Const'ify pci_iommu_ops.

Based upon a similar patch for x86_64 written by
Stephen Hemminger.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/arch/sparc64/kernel/pci_iommu.c b/arch/sparc64/kernel/pci_iommu.c
index 554daab..aefdcc5 100644
--- a/arch/sparc64/kernel/pci_iommu.c
+++ b/arch/sparc64/kernel/pci_iommu.c
@@ -759,7 +759,7 @@
 	spin_unlock_irqrestore(&iommu->lock, flags);
 }
 
-struct pci_iommu_ops pci_sun4u_iommu_ops = {
+const struct pci_iommu_ops pci_sun4u_iommu_ops = {
 	.alloc_consistent		= pci_4u_alloc_consistent,
 	.free_consistent		= pci_4u_free_consistent,
 	.map_single			= pci_4u_map_single,