iommu/hyper-v: Constify hyperv_ir_domain_ops

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.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>