iommu/vt-d: Add present bit check in pasid entry setup helpers

iommu/vt-d: Add present bit check in pasid entry setup helpers

The helper functions should not modify the pasid entries which are still
in use. Add a check against present bit.

Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
Link: https://lore.kernel.org/r/20210817042425.1784279-1-yi.l.liu@intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20210818134852.1847070-10-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>