memory: Store user data pointer in the IOMMU notifiers

This will help developers of ATS-capable devices to track a state.

Signed-off-by: Clement Mathieu--Drif <clement.mathieu--drif@eviden.com>
Message-Id: <20250520071823.764266-9-clement.mathieu--drif@eviden.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/include/system/memory.h b/include/system/memory.h
index fbbf4cf..fc35a0d 100644
--- a/include/system/memory.h
+++ b/include/system/memory.h
@@ -183,6 +183,7 @@
     hwaddr start;
     hwaddr end;
     int iommu_idx;
+    void *opaque;
     QLIST_ENTRY(IOMMUNotifier) node;
 };
 typedef struct IOMMUNotifier IOMMUNotifier;