Reapply "[X86] Flag BroadWell scheduler model as complete"

This reverts commit r320508, in effect re-applying r320308.  Simon has already
reverted the parts that caused the crash that motivated the revert in r320492.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@320512 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed