src: fix compiler warning in udp_wrap.cc

Currently the following compiler warning is generated:
1 warning generated.
../src/udp_wrap.cc:238:12: warning: comparison of integers of different
signs: 'int' and 'uint32_t' (aka 'unsigned int') [-Wsign-compare]
  if (size != args[0].As<Uint32>()->Value()) {
      ~~~~ ^  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.

This commit changes the check to see that the Uint32 value does not
exceed the max int size instead of first casting and then comparing.

PR-URL: nodejs#15402
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>

src/udp_wrap.cc

@@ -234,16 +234,16 @@ void UDPWrap::BufferSize(const FunctionCallbackInfo<Value>& args) {
 
   CHECK(args[0]->IsUint32());
   CHECK(args[1]->IsUint32());
-  int size = static_cast<int>(args[0].As<Uint32>()->Value());
 
-  if (size != args[0].As<Uint32>()->Value()) {
+  if (!args[0]->IsInt32()) {
     if (args[1].As<Uint32>()->Value() == 0)
       return env->ThrowUVException(EINVAL, "uv_recv_buffer_size");
     else
       return env->ThrowUVException(EINVAL, "uv_send_buffer_size");
   }
 
   int err;
+  int size = static_cast<int>(args[0].As<Uint32>()->Value());
   if (args[1].As<Uint32>()->Value() == 0) {
     err = uv_recv_buffer_size(reinterpret_cast<uv_handle_t*>(&wrap->handle_),
                               &size);