iommu: Generalize PASID 0 for normal DMA w/o PASID

PCIe Process address space ID (PASID) is used to tag DMA traffic, it
provides finer grained isolation than requester ID (RID).

For each device/RID, 0 is a special PASID for the normal DMA (no
PASID). This is universal across all architectures that supports PASID,
therefore warranted to be reserved globally and declared in the common
header. Consequently, we can avoid the conflict between different PASID
use cases in the generic code. e.g. SVA and DMA API with PASIDs.

This paved away for device drivers to choose global PASID policy while
continue doing normal DMA.

Noting that VT-d could support none-zero RID/NO_PASID, but currently not
used.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Link: https://lore.kernel.org/r/20230802212427.1497170-2-jacob.jun.pan@linux.intel.com


Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>