sysfs.txt: fix pre-kernfs sysfs_dirent reference

sysfs_dirent went away when kernfs was extracted from sysfs. The reference
to the kobject now lives in a kernfs_node (in the 'priv' member).

See commit 324a56e1 ("kernfs: s/sysfs_dirent/kernfs_node/ and rename
its friends accordingly").
Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/filesystems/sysfs.txt

@@ -40,7 +40,7 @@ ancestors of object hierarchies; i.e. the subsystems the objects
 belong to. 
 
 Sysfs internally stores a pointer to the kobject that implements a
-directory in the sysfs_dirent object associated with the directory. In
+directory in the kernfs_node object associated with the directory. In
 the past this kobject pointer has been used by sysfs to do reference
 counting directly on the kobject whenever the file is opened or closed.
 With the current sysfs implementation the kobject reference count is

Documentation/zh_CN/filesystems/sysfs.txt

@@ -61,7 +61,7 @@ Documentation/kobject.txt 文档以获得更多关于 kobject 接口的
 内核的对象层次到用户空间。sysfs 中的顶层目录代表着内核对象层次的
 共同祖先；例如：某些对象属于某个子系统。
 
-Sysfs 在与其目录关联的 sysfs_dirent 对象中内部保存一个指向实现
+Sysfs 在与其目录关联的 kernfs_node 对象中内部保存一个指向实现
 目录的 kobject 的指针。以前，这个 kobject 指针被 sysfs 直接用于
 kobject 文件打开和关闭的引用计数。而现在的 sysfs 实现中，kobject
 引用计数只能通过 sysfs_schedule_callback() 函数直接修改。