intel_iommu: use the correct memory region for device IOTLB notification

We have a specific memory region for DMAR now, so it's wrong to
trigger the notifier with the root region.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: NJason Wang <jasowang@redhat.com>
Reviewed-by: NPeter Xu <peterx@redhat.com>
Reviewed-by: N\"Michael S. Tsirkin\" <mst@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <1491562755-23867-7-git-send-email-peterx@redhat.com>
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>

hw/i386/intel_iommu.c

@@ -1457,7 +1457,7 @@ static bool vtd_process_device_iotlb_desc(IntelIOMMUState *s,
     entry.iova = addr;
     entry.perm = IOMMU_NONE;
     entry.translated_addr = 0;
-    memory_region_notify_iommu(entry.target_as->root, entry);
+    memory_region_notify_iommu(&vtd_dev_as->iommu, entry);
 
 done:
     return true;