Include EXTENSIBLE_UI in single LCD sanity check (#13306)

Marlin/src/inc/SanityCheck.h

   + ENABLED(SAV_3DGLCD) \
   + ENABLED(OLED_PANEL_TINYBOY2) \
   + ENABLED(ZONESTAR_LCD) \
-  + ENABLED(ULTI_CONTROLLER)
+  + ENABLED(ULTI_CONTROLLER) \
+  + ENABLED(EXTENSIBLE_UI)
   #error "Please select no more than one LCD controller option."
 #endif