iommu/vt-d: Fix to flush cache of PASID directory table

iommu/vt-d: Fix to flush cache of PASID directory table

[ Upstream commit 8a3b8e63f8371c1247b7aa24ff9c5312f1a6948b ]

Even the PCI devices don't support pasid capability, PASID table is
mandatory for a PCI device in scalable mode. However flushing cache
of pasid directory table for these devices are not taken after pasid
table is allocated as the "size" of table is zero. Fix it by
calculating the size by page order.

Found this when reading the code, no real problem encountered for now.

Fixes: 194b3348bdbb ("iommu/vt-d: Fix PASID directory pointer coherency")
Suggested-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Yanfei Xu <yanfei.xu@intel.com>
Link: https://lore.kernel.org/r/20230616081045.721873-1-yanfei.xu@intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>