iommu/vt-d: Multiple descriptors per qi_submit_sync()

iommu/vt-d: Multiple descriptors per qi_submit_sync()

Current qi_submit_sync() only supports single invalidation descriptor
per submission and appends wait descriptor after each submission to
poll the hardware completion. This extends the qi_submit_sync() helper
to support multiple descriptors, and add an option so that the caller
could specify the Page-request Drain (PD) bit in the wait descriptor.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20200516062101.29541-13-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>