ScheduleTree::scheduleDepth: use ScheduleTreeElemBand::nMember

This is the canonical way of determining the number of
scheduling dimensions in a band.

Author: Sven Verdoolaege

tc/core/polyhedral/schedule_tree.cc

@@ -192,7 +192,7 @@ size_t ScheduleTree::scheduleDepth(const ScheduleTree* relativeRoot) const {
     if (!bandElem) {
       continue;
     }
-    depth += bandElem->mupa_.dim(isl::dim_type::set);
+    depth += bandElem->nMember();
   }
   return depth;
 }