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/generic.hpp b/extensions/openpower-pels/generic.hpp
index ff85b03..a03b233 100644
--- a/extensions/openpower-pels/generic.hpp
+++ b/extensions/openpower-pels/generic.hpp
@@ -20,7 +20,7 @@
 {
   public:
     Generic() = delete;
-    ~Generic() = default;
+    ~Generic() override = default;
     Generic(const Generic&) = default;
     Generic& operator=(const Generic&) = default;
     Generic(Generic&&) = default;