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/registry.cpp b/extensions/openpower-pels/registry.cpp
index c8c37f9..a37bb6e 100644
--- a/extensions/openpower-pels/registry.cpp
+++ b/extensions/openpower-pels/registry.cpp
@@ -698,10 +698,10 @@
 
             return entry;
         }
-        catch (const std::exception& e)
+        catch (const std::exception& ex)
         {
             log<level::ERR>("Found invalid message registry field",
-                            entry("ERROR=%s", e.what()));
+                            entry("ERROR=%s", ex.what()));
         }
     }