SPARC64: sg chaining support

This updates the sparc64 iommu/pci dma mappers to sg chaining.

Acked-by: David S. Miller <davem@davemloft.net>

Later updated to newer kernel with unified sparc64 iommu sg handling.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>