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/pel.hpp b/extensions/openpower-pels/pel.hpp
index 631cbdb..460d588 100644
--- a/extensions/openpower-pels/pel.hpp
+++ b/extensions/openpower-pels/pel.hpp
@@ -80,7 +80,7 @@
      *
      * @param[in] data - The PEL data
      */
-    PEL(std::vector<uint8_t>& data);
+    explicit PEL(std::vector<uint8_t>& data);
 
     /**
      * @brief Constructor