iommu/hyper-v: Constify hyperv_ir_domain_ops

The struct hyperv_ir_domain_ops is not modified and can be made const to
allow the compiler to put it in read-only memory.

Before:
   text    data     bss     dec     hex filename
   2916    1180    1120    5216    1460 drivers/iommu/hyperv-iommu.o

After:
   text    data     bss     dec     hex filename
   3044    1052    1120    5216    1460 drivers/iommu/hyperv-iommu.o
Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Acked-by: Wei Liu <wei.liu@kernel.org>
Link: https://lore.kernel.org/r/20200525214958.30015-2-rikard.falkeborn@gmail.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/hyperv-iommu.c

@@ -131,7 +131,7 @@ static int hyperv_irq_remapping_activate(struct irq_domain *domain,
 	return 0;
 }
 
-static struct irq_domain_ops hyperv_ir_domain_ops = {
+static const struct irq_domain_ops hyperv_ir_domain_ops = {
 	.alloc = hyperv_irq_remapping_alloc,
 	.free = hyperv_irq_remapping_free,
 	.activate = hyperv_irq_remapping_activate,