PEL: Fix some cppcheck warnings

This is the first of two commits to fix most of the cppcheck warnings in
the PEL code.  It doesn't fix all of them because some are false
positives and some are just suggestions.

It's broken up into two commits to make them smaller.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I75937797a6920611b136d600e9efd6c694e4209c
diff --git a/extensions/openpower-pels/fru_identity.hpp b/extensions/openpower-pels/fru_identity.hpp
index bcb2956..993b32b 100644
--- a/extensions/openpower-pels/fru_identity.hpp
+++ b/extensions/openpower-pels/fru_identity.hpp
@@ -103,7 +103,7 @@
      * @param[in] procedureFromRegistry - The maintenance procedure name
      *                                    as defined in the message registry.
      */
-    FRUIdentity(const std::string& procedureFromRegistry) :
+    explicit FRUIdentity(const std::string& procedureFromRegistry) :
         FRUIdentity(procedureFromRegistry, CalloutValueType::registryName)
     {
     }