swiotlb: remove SWIOTLB_MAP_ERROR

We can use DMA_MAPPING_ERROR instead, which already maps to the same
value.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Tested-by: Jesper Dangaard Brouer <brouer@redhat.com>
Tested-by: Tony Luck <tony.luck@intel.com>