blockfreq: Move include to .cpp

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208035 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "Walk back commits for unused function parameters - they're still being"

this reapplies 208012 and 208002.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208037 91177308-0d34-0410-b5e6-96231b3b80d8