Update pzemac.h

m_ to pre_

Author: garry0garry

esphome/components/pzemac/pzemac.h

@@ -38,8 +38,8 @@ class PZEMAC : public PollingComponent, public modbus::ModbusDevice {
 
   void reset_energy_();
 
-  uint32_t m_last_update_time_;
-  float m_last_energy_sensor;
+  uint32_t pre_last_update_time_;
+  float pre_last_energy_sensor;
 };
 
 template<typename... Ts> class ResetEnergyAction : public Action<Ts...> {