iommufd/selftest: Explicitly skip tests for inapplicable variant

iommufd/selftest: Explicitly skip tests for inapplicable variant

no_viommu is not applicable for some viommu/vdevice tests. Explicitly
report the skipping, don't do it silently.

Opportunistically adjust the line wrappings after the indentation
changes using git clang-format.

Only add the prints. No functional change intended.

Link: https://patch.msgid.link/r/20250716070349.1807226-7-yilun.xu@linux.intel.com
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>