[llvm-mca] Fix -Wpessimizing-move warnings introduced by r339923.

Reported by buildbot `clang-with-lto-ubuntu` ( build #9858 ).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@339928 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed