iommu/arm-smmu-v3: Support IOMMU_VIOMMU_ALLOC

Add a new driver-type for ARM SMMUv3 to enum iommu_viommu_type. Implement
an arm_vsmmu_alloc().

As an initial step, copy the VMID from s2_parent. A followup series is
required to give the VIOMMU object it's own VMID that will be used in all
nesting configurations.

Link: https://patch.msgid.link/r/8-v4-9e99b76f3518+3a8-smmuv3_nesting_jgg@nvidia.com


Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>