iommu/mediatek: Remove the tlb-ops for v7s

Until now, we have already used the tlb operations from iommu framework,
then the tlb operations for v7s can be removed.

Correspondingly, Switch the paramenter "cookie" to the internal structure.

Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210107122909.16317-8-yong.wu@mediatek.com
Signed-off-by: Will Deacon <will@kernel.org>