Extend the instruction itinerary model to include the ability to indicate the def...

Extend the instruction itinerary model to include the ability to indicate the def and use cycle for each operand. This additional information is optional, so existing itineraries do not need to be changed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@79247 91177308-0d34-0410-b5e6-96231b3b80d8