switch open-coded instances of d_make_root() to new helper

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index c4e2a58..57dae0b 100644
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -309,12 +309,11 @@
 	inode->i_fop = &simple_dir_operations;
 	set_nlink(inode, 2);
 
-	s->s_root = d_alloc_root(inode);
+	s->s_root = d_make_root(inode);
 	if (s->s_root)
 		return 0;
 
 	printk(KERN_ERR "devpts: get root dentry failed\n");
-	iput(inode);
 
 fail:
 	return -ENOMEM;