PEL: Add function to get PEL size

Add a size() function to the PEL class that adds up the size fields
in the header of every PEL section.

This required a fix to some testcases where the size field was wrong in
a header.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I0d70deae116cd3835f2c0ab34e13811da471fb14
diff --git a/extensions/openpower-pels/pel.hpp b/extensions/openpower-pels/pel.hpp
index ccbef91..c3c9f5a 100644
--- a/extensions/openpower-pels/pel.hpp
+++ b/extensions/openpower-pels/pel.hpp
@@ -198,6 +198,13 @@
     std::vector<uint8_t> data() const;
 
     /**
+     * @brief Returns the size of the PEL
+     *
+     * @return size_t The PEL size in bytes
+     */
+    size_t size() const;
+
+    /**
      * @brief Says if the PEL is valid (the sections are all valid)
      *
      * @return bool - if the PEL is valid