memory.c: bugfix - ref counting mismatch in memory_region_find

'address_space_get_flatview' gets a reference to a FlatView.
If the flatview lookup fails, the code returns without
"unreferencing" the view.

Cc: qemu-stable@nongnu.org

Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

memory.c

@@ -1596,6 +1596,7 @@ MemoryRegionSection memory_region_find(MemoryRegion *mr,
     view = address_space_get_flatview(as);
     fr = flatview_lookup(view, range);
     if (!fr) {
+        flatview_unref(view);
         return ret;
     }