iommufd: Put constants for all the uAPI enums

Relying on position in the enum makes it subtly harder when doing merge
resolutions or backporting as it is easy to grab a patch and not notice it
is a uAPI change with a differently ordered enum. This may become a bigger
problem in next cycles when iommu_hwpt_invalidate_data_type and other
per-driver enums have patches flowing through different trees.

So lets start including constants for all the uAPI enums to make this
safer.

No functional change.

Link: https://lore.kernel.org/r/0-v1-2c06ec044924+133-iommufd_uapi_const_jgg@nvidia.com


Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Yi Liu <yi.l.liu@intel.com>
Tested-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>