PEL: Add 'override' to derived destructors

cppcheck complains that it is overriding a virtual function in the base
class but isn't marked with override.

Change-Id: I4e03f0524987427e3742672d27b86c71943fab5b
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/extensions/openpower-pels/data_interface.hpp b/extensions/openpower-pels/data_interface.hpp
index 41a6d86..29ba22e 100644
--- a/extensions/openpower-pels/data_interface.hpp
+++ b/extensions/openpower-pels/data_interface.hpp
@@ -690,7 +690,7 @@
 {
   public:
     DataInterface() = delete;
-    ~DataInterface() = default;
+    ~DataInterface() override = default;
     DataInterface(const DataInterface&) = delete;
     DataInterface& operator=(const DataInterface&) = delete;
     DataInterface(DataInterface&&) = delete;