sysfs: move struct sysfs_dirent to private header

struct sysfs_dirent is private to the fs/sysfs/ subtree.  It is
not even referenced as an opaque structure outside of that subtree.

The following patch moves the declaration from include/linux/sysfs.h to
fs/sysfs/sysfs.h, making it clearer that nothing else in the kernel
dereferences it.

I have been running this patch for years.  Please integrate and forward
upstream if there are no objections.

From: "Adam J. Richter" <adam@yggdrasil.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

fs/sysfs/sysfs.h

+struct sysfs_dirent {
+	atomic_t		s_count;
+	struct list_head	s_sibling;
+	struct list_head	s_children;
+	void 			* s_element;
+	int			s_type;
+	umode_t			s_mode;
+	struct dentry		* s_dentry;
+	struct iattr		* s_iattr;
+	atomic_t		s_event;
+};
 
 extern struct vfsmount * sysfs_mount;
 extern struct kmem_cache *sysfs_dir_cachep;

include/linux/sysfs.h

@@ -17,6 +17,7 @@
 struct kobject;
 struct module;
 struct nameidata;
+struct dentry;
 
 struct attribute {
 	const char		* name;
@@ -68,18 +69,6 @@ struct sysfs_ops {
 	ssize_t	(*store)(struct kobject *,struct attribute *,const char *, size_t);
 };
 
-struct sysfs_dirent {
-	atomic_t		s_count;
-	struct list_head	s_sibling;
-	struct list_head	s_children;
-	void 			* s_element;
-	int			s_type;
-	umode_t			s_mode;
-	struct dentry		* s_dentry;
-	struct iattr		* s_iattr;
-	atomic_t		s_event;
-};
-
 #define SYSFS_ROOT		0x0001
 #define SYSFS_DIR		0x0002
 #define SYSFS_KOBJ_ATTR 	0x0004