[MLIR][NFC] Insert const_cast to avoid warning

[rriddle]

What is the warning?

[uenoku]

In D71853#1795658, @rriddle wrote:

What is the warning?

llvm-project/mlir/include/mlir/IR/Value.h:112:47: warning: cast from 'const mlir::Value *' to 'mlir::Value *' drops const qualifier [-Wcast-qual]
  Value *operator->() const { return (Value *)this; }

Like this

mlir/include/mlir/IR/Value.h

template <typename U> U cast() const {
     assert(isa<U>());
     return U(impl);
   }
 
   /// Temporary methods to enable transition of Value to being used as a
   /// value-type.
   /// TODO(riverriddle) Remove these when all usages have been removed.
   Value operator*() const { return *this; }
-  Value *operator->() const { return (Value *)this; }
+  Value *operator->() const { return const_cast<Value *>(this); }
 
   operator bool() const { return impl; }
   bool operator==(const Value &other) const { return impl == other.impl; }
   bool operator!=(const Value &other) const { return !(*this == other); }
 
   /// Return the kind of this value.
   Kind getKind() const { return (Kind)impl->typeAndKind.getInt(); }
 

mlir/include/mlir/Pass/PassOptions.h

void print(raw_ostream &os) final {
       auto printElementFn = [&](const DataType &value) {
         printValue(os, this->getParser(), value);
       };
       interleave(*this, os, printElementFn, ",");
     }
 
     /// Copy the value from the given option into this one.
     void copyValueFrom(const OptionBase &other) final {
-      (*this) = ArrayRef<DataType>((ListOption<DataType> &)other);
+      (*this) = ArrayRef<DataType>(
+          (ListOption<DataType> &)(const_cast<OptionBase &>(other)));
     }
   };
 
   PassOptions() = default;
 
   /// Copy the option values from 'other' into 'this', where 'other' has the
   /// same options as 'this'.
   void copyOptionValuesFrom(const PassOptions &other);