fix(lsc_smart_ceiling_light): expose dp 20 master switch

Apparently required to have both lights stay off.

Used as an availability flag on the light entities, to avoid mistakenly
adjusting them while the master is off.

Comment on PR #2359

custom_components/tuya_local/devices/lsc_smart_ceiling_light.yaml

@@ -3,12 +3,21 @@ products:
   - id: bwyutsrcsnwf3p5o
     manufacturer: LSC Smart Connect
 entities:
+  - entity: switch
+    dps:
+      - id: 20
+        type: boolean
+        name: switch
+
   - entity: light
     icon: mdi:circle
     dps:
       - id: 63
         type: boolean
         name: switch
+      - id: 20
+        type: boolean
+        name: available
       - id: 22
         name: brightness
         type: integer
@@ -33,6 +42,9 @@ entities:
       - id: 54
         type: boolean
         name: switch
+      - id: 20
+        type: boolean
+        name: available
       - id: 24
         name: rgbhsv
         type: hex