[llvm-mca] Move definitions in FetchStage.cpp inside namespace mca. NFC

Also, get rid of a redundant include in FetchStage.h and FetchStage.cpp.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@332468 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed