iommu: Add IOMMU_CAP_ENFORCE_CACHE_COHERENCY

This queries if a domain linked to a device should expect to support
enforce_cache_coherency() so iommufd can negotiate the rules for when a
domain should be shared or not.

For iommufd a device that declares IOMMU_CAP_ENFORCE_CACHE_COHERENCY will
not be attached to a domain that does not support it.

Link: https://lore.kernel.org/r/1-v6-a196d26f289e+11787-iommufd_jgg@nvidia.com
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Yi Liu <yi.l.liu@intel.com>
Tested-by: Lixiao Yang <lixiao.yang@intel.com>
Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>
Tested-by: Yu He <yu.he@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>