iommu: remove the unused dev_has_feat method

This method is never actually called.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20220708080616.238833-2-hch@lst.de


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