[llvm-mca] Use an ordered map to collect hardware statistics. NFC.

Histogram entries are now ordered by key.  This should improves their
readability when statistics are printed.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@334961 91177308-0d34-0410-b5e6-96231b3b80d8
10 files changed