Revert "sysfs: Kill nlink counting."

This reverts commit 524b6c5b39.

It has shown to break userspace tools, which is not acceptable.

Reported-by: Jiri Slaby <jslaby@suse.cz>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/sysfs/sysfs.h

@@ -19,6 +19,7 @@ struct sysfs_open_dirent;
 struct sysfs_elem_dir {
 	struct kobject		*kobj;
 
+	unsigned long		subdirs;
 	/* children rbtree starts here and goes through sd->s_rb */
 	struct rb_root		children;
 };