[FIX][DFSv2][ELMFAT]解决dfs_elm_unlink在FF_VOLUMES为1时赋值drivers_fn引用未定义变量导致编译报错的问题

components/dfs/dfs_v2/filesystems/elmfat/dfs_elm.c

@@ -784,7 +784,7 @@ int dfs_elm_unlink(struct dfs_dentry *dentry)
     rt_snprintf(drivers_fn, 256, "%d:%s", vol, dentry->pathname);
 #else
     const char *drivers_fn;
-    drivers_fn = path;
+    drivers_fn = dentry->pathname;
 #endif
 
     result = f_unlink(drivers_fn);