iommufd/selftest: Add IOMMU_VEVENTQ_ALLOC test coverage

Trigger vEVENTs by feeding an idev ID and validating the returned output
virt_ids whether they equal to the value that was set to the vDEVICE.

Link: https://patch.msgid.link/r/e829532ec0a3927d61161b7674b20e731ecd495b.1741719725.git.nicolinc@nvidia.com


Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>