iommu/vt-d: Add iotlb flush for nested domain

This implements the .cache_invalidate_user() callback to support iotlb
flush for nested domain.

Link: https://lore.kernel.org/r/20240111041015.47920-9-yi.l.liu@intel.com
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Co-developed-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>