Revert "dma-iommu: add iommu_dma_opt_mapping_size()"

This reverts commit aa4cc17b which is
commit 6d9870b7 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: Ia45a90ff8b22055f8011eadcc629577873142bd7
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>