The aim of this machvec is to support devices with < 32-bit dma
masks.  But given that ia64 only has a ZONE_DMA32 and not a ZONE_DMA
that isn't supported by swiotlb either.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lkml.kernel.org/r/20190813072514.23299-21-hch@lst.deSigned-off-by: Tony Luck <tony.luck@intel.com>