[multiple] Add missing device_class to sensor schemas (batch 2) (#15487)

Co-authored-by: J. Nick Koston <nick@koston.org>

esphome/components/debug/sensor.py

@@ -8,6 +8,7 @@ from esphome.const import (
     CONF_FRAGMENTATION,
     CONF_FREE,
     CONF_LOOP_TIME,
+    DEVICE_CLASS_FREQUENCY,
     ENTITY_CATEGORY_DIAGNOSTIC,
     ICON_COUNTER,
     ICON_TIMER,
@@ -102,6 +103,7 @@ CONFIG_SCHEMA = {
             unit_of_measurement=UNIT_HERTZ,
             icon="mdi:speedometer",
             accuracy_decimals=0,
+            device_class=DEVICE_CLASS_FREQUENCY,
             entity_category=ENTITY_CATEGORY_DIAGNOSTIC,
             state_class=STATE_CLASS_MEASUREMENT,
         ),