PEL: Remove Section::validate() virtual func

There is no need for the validate() function that every PEL section uses
to be virtual, because it is always called directly by the class it's
defined in.

Also, cppcheck was complaining that constructors, where validate() is
called, can't call virtual functions anyway.

Tested:
Unit tests pass

Change-Id: I7190a5299baa85f7956963e21189da0f4c62b68a
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/extensions/openpower-pels/failing_mtms.hpp b/extensions/openpower-pels/failing_mtms.hpp
index 4206b6a..71722d9 100644
--- a/extensions/openpower-pels/failing_mtms.hpp
+++ b/extensions/openpower-pels/failing_mtms.hpp
@@ -96,7 +96,7 @@
      *
      * Updates _valid (in Section) with the results.
      */
-    void validate() override;
+    void validate();
 
     /**
      * @brief Fills in the object from the stream data