[NFC][LLVM] Namespace cleanup in Reg2Mem.cpp (#163765)

llvm/lib/Transforms/Scalar/Reg2Mem.cpp

diff --git a/llvm/lib/Transforms/Scalar/Reg2Mem.cpp b/llvm/lib/Transforms/Scalar/Reg2Mem.cpp
index 30b27cb..7646624 100644
--- a/llvm/lib/Transforms/Scalar/Reg2Mem.cpp
+++ b/llvm/lib/Transforms/Scalar/Reg2Mem.cpp
@@ -107,9 +107,7 @@
   return PA;
 }
 
-namespace llvm {
-
-void initializeRegToMemWrapperPassPass(PassRegistry &);
+namespace {
 
 class RegToMemWrapperPass : public FunctionPass {
 public:
@@ -136,7 +134,7 @@
     return N != 0 || Changed;
   }
 };
-} // namespace llvm
+} // namespace
 
 INITIALIZE_PASS_BEGIN(RegToMemWrapperPass, "reg2mem", "", true, true)
 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass);