Currently, the duplicated sg table is freed in the detach() and
the error path of map_dma_buf() ion's dma_buf_ops.
If a call to dma_buf_map_attachment() fails, the importer is
expected to call dma_buf_detach() to remove the attachment. This
will result in us trying to free the duped sg table twice.
Don't call free_duped_table() in ion_map_dma_buf() to avoid this.