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/extended_user_data.hpp b/extensions/openpower-pels/extended_user_data.hpp
index 086dc9b..8822e7b 100644
--- a/extensions/openpower-pels/extended_user_data.hpp
+++ b/extensions/openpower-pels/extended_user_data.hpp
@@ -24,7 +24,7 @@
 {
   public:
     ExtendedUserData() = delete;
-    ~ExtendedUserData() = default;
+    ~ExtendedUserData() override = default;
     ExtendedUserData(const ExtendedUserData&) = default;
     ExtendedUserData& operator=(const ExtendedUserData&) = default;
     ExtendedUserData(ExtendedUserData&&) = default;