[P056] Fix ReadAverage() output params passed by value, always returning 0

Regression from #5369: P056_data_struct::ReadAverage() took float pm25/pm10 by value, so the averaged values never reached the caller and the task values stayed 0. Pass them by reference like CjkSDS011::ReadAverage().

src/src/PluginStructs/P056_data_struct.cpp

@@ -49,7 +49,7 @@ float P056_data_struct::GetPM10_() {
   }
 }
 
-bool P056_data_struct::ReadAverage(float pm25, float pm10) {
+bool P056_data_struct::ReadAverage(float& pm25, float& pm10) {
   if (isInitialized()) {
     return this->SDS->ReadAverage(pm25, pm10);
   } else {

src/src/PluginStructs/P056_data_struct.h

@@ -17,8 +17,8 @@ struct P056_data_struct : public PluginTaskData_base {
   bool  available();
   float GetPM2_5();
   float GetPM10_();
-  bool  ReadAverage(float pm25,
-                    float pm10);
+  bool  ReadAverage(float& pm25,
+                    float& pm10);
   void  SetWorkingPeriod(int minutes);
 
 private: