iommu: remove iommu_dev_feature_enabled

Remove the unused iommu_dev_feature_enabled function.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20220708080616.238833-3-hch@lst.de


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