[llvm-mca] Move namespace mca inside llvm::

Summary: This allows to remove `using namespace llvm;` in those *.cpp files

When we want to revisit the decision (everything resides in llvm::mca::*) in the future, we can move things to a nested namespace of llvm::mca::, to conceptually make them separate from the rest of llvm::mca::*

Reviewers: andreadb, mattd

Reviewed By: andreadb

Subscribers: javed.absar, tschuett, gbedwell, llvm-commits

Differential Revision: https://reviews.llvm.org/D53407

llvm-svn: 345612
diff --git a/llvm/tools/llvm-mca/Views/InstructionInfoView.cpp b/llvm/tools/llvm-mca/Views/InstructionInfoView.cpp
index 0a97e56..5016afb 100644
--- a/llvm/tools/llvm-mca/Views/InstructionInfoView.cpp
+++ b/llvm/tools/llvm-mca/Views/InstructionInfoView.cpp
@@ -14,10 +14,9 @@
 
 #include "Views/InstructionInfoView.h"
 
+namespace llvm {
 namespace mca {
 
-using namespace llvm;
-
 void InstructionInfoView::printView(raw_ostream &OS) const {
   std::string Buffer;
   raw_string_ostream TempStream(Buffer);
@@ -87,3 +86,4 @@
   OS << Buffer;
 }
 } // namespace mca.
+} // namespace llvm