clang-tidy: enable clang-tidy

Enable the first check: readability-identifier-naming

Also fixed all check failures. The renaming is done by clang-tidy
automatically.

Tested:
1. compiles, no clang-tidy failures
2. tested on QEMU, Redfish is working correctly
3. tested on s7106, Redfish is working correctly; certificates can be
   retrieved.

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: I3c5c9ca734146a94f4e0433ed8c1ae84173288c5
diff --git a/argument.cpp b/argument.cpp
index ba4ebbc..5733e09 100644
--- a/argument.cpp
+++ b/argument.cpp
@@ -22,7 +22,7 @@
     CLI11_PARSE(app, argc, argv);
     phosphor::certs::CertificateType type =
         phosphor::certs::stringToCertificateType(arguments.typeStr);
-    if (type == phosphor::certs::CertificateType::Unsupported)
+    if (type == phosphor::certs::CertificateType::unsupported)
     {
         std::cerr << "type not specified or invalid." << std::endl;
         return 1;