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.cpp b/extensions/openpower-pels/json_utils.cpp
index cd41804..871bd32 100644
--- a/extensions/openpower-pels/json_utils.cpp
+++ b/extensions/openpower-pels/json_utils.cpp
@@ -193,5 +193,15 @@
         jsonStr.append("[],\n");
     }
 }
+
+std::string trimEnd(std::string s)
+{
+    const char* t = " \t\n\r\f\v";
+    if (s.find_last_not_of(t) != std::string::npos)
+    {
+        s.erase(s.find_last_not_of(t) + 1);
+    }
+    return s;
+}
 } // namespace pels
 } // namespace openpower