add exfat config

components/dfs/Kconfig

@@ -148,6 +148,10 @@ endif
             range 0 1000000
             default 3000
             depends on RT_DFS_ELM_REENTRANT
+
+        config RT_DFS_ELM_USE_EXFAT
+        bool "Enable RT_DFS_ELM_USE_EXFAT"
+        default n
         endmenu
     endif
 
@@ -164,10 +168,6 @@ endif
         default n
         # select PKG_USING_ZLIB
 
-    config RT_DFS_ELM_USE_EXFAT
-        bool "Enable RT_DFS_ELM_USE_EXFAT"
-        default n
-
 if RT_USING_DFS_V1
     config RT_USING_DFS_RAMFS
         bool "Enable RAM file system"