[clang-format][NFC] Include TableGen in enum->string mapping used for debugging

Running `clang-format -debug` prints "Unknown" for tablegen files because of this missing mapping, even though it is recognized as a tablegen file.

llvm-svn: 356097

clang/include/clang/Format/Format.h

@@ -2089,6 +2089,8 @@ inline StringRef getLanguageName(FormatStyle::LanguageKind Language) {
     return "JavaScript";
   case FormatStyle::LK_Proto:
     return "Proto";
+  case FormatStyle::LK_TableGen:
+    return "TableGen";
   case FormatStyle::LK_TextProto:
     return "TextProto";
   default: