iommu/amd: Remove outdated comment

Comment is not related to amd_iommu_ops variable.

Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Link: https://lore.kernel.org/r/20220912063248.7909-5-vasant.hegde@amd.com


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