add exfat config

components/dfs/Kconfig

@@ -152,6 +152,7 @@ endif
         config RT_DFS_ELM_USE_EXFAT
             bool "Enable RT_DFS_ELM_USE_EXFAT"
             default n
+            depends on RT_DFS_ELM_USE_LFN >= 1
         endmenu
     endif