iommu/ipmmu-vmsa: Make ipmmu_gather_ops const

Make these const as they are not modified anywhere.
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/ipmmu-vmsa.c

@@ -295,7 +295,7 @@ static void ipmmu_tlb_add_flush(unsigned long iova, size_t size,
 	/* The hardware doesn't support selective TLB flush. */
 }
 
-static struct iommu_gather_ops ipmmu_gather_ops = {
+static const struct iommu_gather_ops ipmmu_gather_ops = {
 	.tlb_flush_all = ipmmu_tlb_flush_all,
 	.tlb_add_flush = ipmmu_tlb_add_flush,
 	.tlb_sync = ipmmu_tlb_flush_all,