iommu/vt-d: Remove duplicate identity domain flag

iommu/vt-d: Remove duplicate identity domain flag

The iommu_domain data structure already has the "type" field to keep the
type of a domain. It's unnecessary to have the DOMAIN_FLAG_STATIC_IDENTITY
flag in the vt-d implementation. This cleans it up with no functionality
change.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20210926114535.923263-1-baolu.lu@linux.intel.com
Link: https://lore.kernel.org/r/20211014053839.727419-4-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>