iommu/dma: Fix leak in non-contiguous API

iommu/dma: Fix leak in non-contiguous API

Currently, iommu_dma_alloc_noncontiguous() allocates a
struct dma_sgt_handle object to hold some state needed for
iommu_dma_free_noncontiguous().

However, the handle is neither freed nor returned explicitly by
the ->alloc_noncontiguous method, and therefore seems leaked.
This was found by code inspection, so please review carefully and test.

As a side note, it appears the struct dma_sgt_handle type is exposed
to users of the DMA-API by linux/dma-map-ops.h, but is has no users
or functions returning the type explicitly.

This may indicate it's a good idea to move the struct dma_sgt_handle type
to drivers/iommu/dma-iommu.c. The decision is left to maintainers :-)

Cc: stable@vger.kernel.org
Fixes: e817ee5f2f95c ("dma-iommu: implement ->alloc_noncontiguous")
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210723010552.50969-1-ezequiel@collabora.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>