[TableGen] Remove unneeded namespace around a function. Just put llvm:: on the definition since it's already declared in a header file.

llvm-svn: 238178
diff --git a/llvm/lib/TableGen/Main.cpp b/llvm/lib/TableGen/Main.cpp
index d59cd21..17556a2 100644
--- a/llvm/lib/TableGen/Main.cpp
+++ b/llvm/lib/TableGen/Main.cpp
@@ -70,9 +70,7 @@
   return 0;
 }
 
-namespace llvm {
-
-int TableGenMain(char *argv0, TableGenMainFn *MainFn) {
+int llvm::TableGenMain(char *argv0, TableGenMainFn *MainFn) {
   RecordKeeper Records;
 
   // Parse the input file.
@@ -120,5 +118,3 @@
   Out.keep();
   return 0;
 }
-
-}