iommu: remove unused priv field from struct iommu_ops

The priv field from iommu_ops is a hangover from the of_dma_configure
series and isn't actually used. Remove it before it has chance to
spread.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>