fs: Support the root file system attributes(mode, uid, gid and time)

Note: all attributes is guarded by PSEUDOFS_ATTRIBUTES to save the space

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
Change-Id: I664d60382e356068fd920f08aca5b4a49d8d92a9

fs/romfs/fs_romfs.c

@@ -225,10 +225,6 @@ static int romfs_open(FAR struct file *filep, FAR const char *relpath,
       goto errout_with_semaphore;
     }
 
-#ifdef CONFIG_FILE_MODE
-# warning "Missing check for privileges based on inode->i_mode"
-#endif
-
   /* Create an instance of the file private data to describe the opened
    * file.
    */