Fixed incorrect Init logic for ESP-NN Conv2D Kernel

- Init method was initialisating a persistent buffer equal to size of OpDataConv while the correct size would be that of NodeData which is used by ESP-NN
- This had knock-on effects in other places, e.g. when running quantized MobileNetV2 model this led to the Softmax Node's beta param getting overridden.

Author: ShardulNalegave

tensorflow/lite/micro/kernels/esp_nn/conv.cc

@@ -45,7 +45,7 @@ struct NodeData {
 
 static void* Init(TfLiteContext* context, const char* buffer, size_t length) {
   TFLITE_DCHECK(context->AllocatePersistentBuffer != nullptr);
-  return context->AllocatePersistentBuffer(context, sizeof(OpDataConv));
+  return context->AllocatePersistentBuffer(context, sizeof(NodeData));
 }
 
 static TfLiteStatus Prepare(TfLiteContext* context, TfLiteNode* node) {