iommu/vt-d: Set context field after value initialized

Otherwise, the translation type field of a context entry for
a PCI device will always be 0. All translated DMA requests
will be blocked by IOMMU. As the result, the PCI devices with
PCI ATS (device IOTBL) support won't work as expected.

Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Suggested-by: Kevin Tian <kevin.tian@intel.com>
Fixes: 7373a8cc ("iommu/vt-d: Setup context and enable RID2PASID support")
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>