misched: TargetSchedule interface for machine resources.

misched: TargetSchedule interface for machine resources.

Expose the processor resources defined by the machine model to the
scheduler and other clients through the TargetSchedule interface.

Normalize each resource count with respect to other kinds of
resources. This allows scheduling heuristics to balance resources
against other kinds of resources and latency.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167444 91177308-0d34-0410-b5e6-96231b3b80d8