iommu: Cleanup comments for dev_enable/disable_feat

The dev_enable/disable_feat ops have been removed by commit
<f984fb09> ("iommu: Remove iommu_dev_enable/disable_feature()").
Cleanup the comments to make the code clean.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20250430025249.2371751-1-baolu.lu@linux.intel.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>