[turbofan] Fix bitfield size in regalloc (after moving to MachineRepresentation).

src/compiler/register-allocator.h

Index: src/compiler/register-allocator.h
diff --git a/src/compiler/register-allocator.h b/src/compiler/register-allocator.h
index a5d46b058d72146f3707f586e686b724f9e2bd9f..b3b75fd57ef63d66ca28f6110e0b29519983c858 100644
--- a/src/compiler/register-allocator.h
+++ b/src/compiler/register-allocator.h
@@ -430,7 +430,7 @@ class LiveRange : public ZoneObject {
 
   typedef BitField<bool, 0, 1> SpilledField;
   typedef BitField<int32_t, 6, 6> AssignedRegisterField;
-  typedef BitField<MachineRepresentation, 12, 15> RepresentationField;
+  typedef BitField<MachineRepresentation, 12, 8> RepresentationField;
 
   // Unique among children and splinters of the same virtual register.
   int relative_id_;