sysfs, kernfs: introduce kernfs_rename[_ns]()

Introduce kernfs rename interface, krenfs_rename[_ns]().

This is just rename of sysfs_rename().  No functional changes.
Function comment is added to kernfs_rename_ns() and @new_parent_sd is
renamed to @new_parent for consistency with other kernfs interfaces.

v2: Dummy implementation for !CONFIG_SYSFS updated to return -ENOSYS.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index 41138e9..0922c53 100644
--- a/fs/sysfs/symlink.c
+++ b/fs/sysfs/symlink.c
@@ -226,7 +226,7 @@
 	if (sd->s_symlink.target_sd->s_dir.kobj != targ)
 		goto out;
 
-	result = sysfs_rename(sd, parent_sd, new, new_ns);
+	result = kernfs_rename_ns(sd, parent_sd, new, new_ns);
 
 out:
 	sysfs_put(sd);