hw/arm/virt: Add an SMMU_IO_LEN macro

hw/arm/virt: Add an SMMU_IO_LEN macro

This is useful as the subsequent support for new SMMUv3 dev will also
use the same.

Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Donald Dutile <ddutile@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Nathan Chen <nathanc@nvidia.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Signed-off-by: Shameer Kolothum <skolothumtho@nvidia.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Message-id: 20250829082543.7680-6-skolothumtho@nvidia.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>