Merge pull request #7715 from GMagician/bugfix-2.0.x

[PR] [Marlin 2.0] Fix compiler warning message

Marlin/src/module/configuration_store.cpp

     #endif
 
     if (!eeprom_error) {
-      const int eeprom_size = eeprom_index;
+      #if ENABLED(EEPROM_CHITCHAT)
+        const int eeprom_size = eeprom_index;
+      #endif
 
       const uint16_t final_crc = working_crc;