Asakuki diffuser, UStellar light bar: avoid hex with mappings

Issue #1629

Review found same issue in these two device configs.

custom_components/tuya_local/devices/asakuki_diffuser.yaml

@@ -93,7 +93,7 @@ secondary_entities:
     category: config
     dps:
       - id: 108
-        type: hex
+        type: string
         name: option
         mapping:
           - dps_val: "ff00000064ff"

custom_components/tuya_local/devices/ustellar_ut99911_rgb.yaml

@@ -76,7 +76,7 @@ secondary_entities:
     category: config
     dps:
       - id: 102
-        type: hex
+        type: string
         name: option
         optional: true
         mapping: