PEL: Print Failing MTMS section into JSON

Remove any trailing whitespace for serial number.

"Failing MTMS": {
    "Section Version":          "1",
    "Sub-section type":         "0",
    "Created by":               "0x4552",
    "Machine Type Model":       "OPWR-131",
    "Serial Number":            "1318ABA"
},

Testing: Manually run peltool and verified output. All unit tests
passed.
Signed-off-by: Harisuddin Mohamed Isa <harisuddin@gmail.com>
Change-Id: I7a05790bdf406ef6d7946ffae831a45ee6dd5cda
diff --git a/extensions/openpower-pels/json_utils.hpp b/extensions/openpower-pels/json_utils.hpp
index f3fb767..e122f47 100644
--- a/extensions/openpower-pels/json_utils.hpp
+++ b/extensions/openpower-pels/json_utils.hpp
@@ -76,5 +76,12 @@
     return numString;
 }
 
+/**
+ * @brief helper function to trim trailing whitespaces
+ * @return std::string - trimmed string
+ * @param[in] std::string - string to trim
+ */
+std::string trimEnd(std::string s);
+
 } // namespace pels
 } // namespace openpower