Add a default NoItinerary class for targets to use.

llvm-svn: 25670
diff --git a/llvm/lib/Target/TargetSchedule.td b/llvm/lib/Target/TargetSchedule.td
index 8911844..8ac537f 100644
--- a/llvm/lib/Target/TargetSchedule.td
+++ b/llvm/lib/Target/TargetSchedule.td
@@ -47,6 +47,7 @@
 // instruction information.
 //
 class InstrItinClass;
+def NoItinerary : InstrItinClass;
 
 //===----------------------------------------------------------------------===//
 // Instruction itinerary data - These values provide a runtime map of an