AAUTO-303 vehicle/nanopb: Added missing string callback. In Android12 user

 space is sending message with string callback. Without this update is
kernel crashing.

drivers/mxc/vehicle/vehicle_protocol_callback.c

@@ -99,9 +99,10 @@ bool decode_value_callback(pb_istream_t *stream, const pb_field_t *field, void *
 	propvalue.int32_values.arg = &data->value;
 	propvalue.float_values.funcs.decode = &decode_float_values_callback;
 	propvalue.float_values.arg = &data->value;
+	propvalue.string_value.funcs.decode = &decode_config_string_callback;
+	propvalue.string_value.arg = &data->value;
 	/*hvac have not use this field now.*/
 	//propvalue.int64_values.funcs.decode = &decode_int64_values_callback;
-	//propvalue.string_value.funcs.decode = &decode_config_string_callback;
 	//propvalue.bytes_value.funcs.decode = &decode_config_string_callback;
 
 	if (!pb_decode(stream, emulator_VehiclePropValue_fields, &propvalue))