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/service_indicators.hpp b/extensions/openpower-pels/service_indicators.hpp
index 5375e13..13e6355 100644
--- a/extensions/openpower-pels/service_indicators.hpp
+++ b/extensions/openpower-pels/service_indicators.hpp
@@ -57,7 +57,7 @@
 {
   public:
     LightPath() = delete;
-    virtual ~LightPath() = default;
+    ~LightPath() override = default;
     LightPath(const LightPath&) = default;
     LightPath& operator=(const LightPath&) = delete;
     LightPath(LightPath&&) = delete;