[core] Make LOG_ENTITY_ICON a no-op when icons are compiled out

When USE_ENTITY_ICON is not defined, LOG_ENTITY_ICON and log_entity_icon
are now completely compiled out rather than calling a function that
checks an always-empty icon reference.

esphome/core/entity_base.cpp

@@ -152,11 +152,13 @@ void EntityBase_UnitOfMeasurement::set_unit_of_measurement(const char *unit_of_m
   this->unit_of_measurement_ = unit_of_measurement;
 }
 
+#ifdef USE_ENTITY_ICON
 void log_entity_icon(const char *tag, const char *prefix, const EntityBase &obj) {
   if (!obj.get_icon_ref().empty()) {
     ESP_LOGCONFIG(tag, "%s  Icon: '%s'", prefix, obj.get_icon_ref().c_str());
   }
 }
+#endif
 
 void log_entity_device_class(const char *tag, const char *prefix, const EntityBase_DeviceClass &obj) {
   if (!obj.get_device_class_ref().empty()) {

esphome/core/entity_base.h

@@ -231,8 +231,12 @@ class EntityBase_UnitOfMeasurement {  // NOLINT(readability-identifier-naming)
 };
 
 /// Log entity icon if set (for use in dump_config)
+#ifdef USE_ENTITY_ICON
 #define LOG_ENTITY_ICON(tag, prefix, obj) log_entity_icon(tag, prefix, obj)
 void log_entity_icon(const char *tag, const char *prefix, const EntityBase &obj);
+#else
+#define LOG_ENTITY_ICON(tag, prefix, obj)
+#endif
 /// Log entity device class if set (for use in dump_config)
 #define LOG_ENTITY_DEVICE_CLASS(tag, prefix, obj) log_entity_device_class(tag, prefix, obj)
 void log_entity_device_class(const char *tag, const char *prefix, const EntityBase_DeviceClass &obj);