fix(dewall_evcharger): mark dps 155, 156 as optional

Minor features, apparently not reported by some devices, or in some configurations.

Issue #6106

custom_components/tuya_local/devices/dewall_evcharger.yaml

@@ -142,6 +142,7 @@ entities:
     dps:
       - id: 155
         type: boolean
+        optional: true
         name: switch
       - id: 157
         type: integer
@@ -158,6 +159,7 @@ entities:
     dps:
       - id: 156
         type: boolean
+        optional: true
         name: switch
   - entity: number
     name: Operating state