[mlir] Fix unused var warning in the IR/MemRefOps.cpp

[rdzhabarov]

Summary

Fix unused var compiler warning.

mlir/lib/Dialect/MemRef/IR/MemRefOps.cpp

LogicalResult matchAndRewrite(AllocaScopeOp op,
 
     while (!lastParentWithoutScope->getParentOp()
                 ->hasTrait<OpTrait::AutomaticAllocationScope>()) {
       lastParentWithoutScope = lastParentWithoutScope->getParentOp();
       if (!lastParentWithoutScope ||
           !lastNonTerminatorInRegion(lastParentWithoutScope))
         return failure();
     }
-    Operation *scope = lastParentWithoutScope->getParentOp();
-    assert(scope->hasTrait<OpTrait::AutomaticAllocationScope>());
+    assert(lastParentWithoutScope->getParentOp()
+               ->hasTrait<OpTrait::AutomaticAllocationScope>());
 
     Region *containingRegion = nullptr;
     for (auto &r : lastParentWithoutScope->getRegions()) {
       if (r.isAncestor(op->getParentRegion())) {
         assert(containingRegion == nullptr &&
                "only one region can contain the op");
         containingRegion = &r;
       }