ia64/sba_iommu: return error code from sba_map_sg_attrs()

The .map_sg() op now expects an error code instead of zero on failure.

In the case of a dma_mapping_error() return -EIO as the actual cause
is opaque here.

sba_coalesce_chunks() may only presently fail if sba_alloc_range()
fails, which in turn only fails if the iommu is out of mapping
resources, hence a -ENOMEM is used in that case.

Signed-off-by: Martin Oliveira <martin.oliveira@eideticom.com>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Niklas Schnelle <schnelle@linux.ibm.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>