Revert "powerpc/pseries/iommu: Don't use dma_iommu_ops on secure guests"

Revert "powerpc/pseries/iommu: Don't use dma_iommu_ops on secure guests"

This reverts commit edea902c1c1efb855f77e041f9daf1abe7a9768a.

At the time the change allowed direct DMA ops for secure VMs; however
since then we switched on using SWIOTLB backed with IOMMU (direct mapping)
and to make this work, we need dma_iommu_ops which handles all cases
including TCE mapping I/O pages in the presence of an IOMMU.

Fixes: edea902c1c1e ("powerpc/pseries/iommu: Don't use dma_iommu_ops on secure guests")
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
[aik: added "revert" and "fixes:"]
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Tested-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191216041924.42318-2-aik@ozlabs.ru