Arlec panel heater v2: use capitalised presets in protocol

The original report had no info on the presets, so I guessed based on most common practice
that they would be lower case, "eco", "comfort", "af", but after a user captured the
diagnostics, they in fact turn out to be capitalised, with Antifrost spelt out in full,
and ECO in all caps.

Issue #578

custom_components/tuya_local/devices/arlec_panel_heater_v2.yaml

@@ -29,11 +29,11 @@ primary_entity:
       name: preset_mode
       type: string
       mapping:
-        - dps_val: "eco"
+        - dps_val: "ECO"
           value: "Eco"
-        - dps_val: "comfort"
+        - dps_val: "Comfort"
           value: "Comfort"
-        - dps_val: "af"
+        - dps_val: "Antifrost"
           value: "Anti-frost"
 secondary_entities:
   - entity: lock