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

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/s390/hypfs/inode.c b/arch/s390/hypfs/inode.c
index 8a2a887..6a2cb56 100644
--- a/arch/s390/hypfs/inode.c
+++ b/arch/s390/hypfs/inode.c
@@ -293,11 +293,9 @@
 		return -ENOMEM;
 	root_inode->i_op = &simple_dir_inode_operations;
 	root_inode->i_fop = &simple_dir_operations;
-	sb->s_root = root_dentry = d_alloc_root(root_inode);
-	if (!root_dentry) {
-		iput(root_inode);
+	sb->s_root = root_dentry = d_make_root(root_inode);
+	if (!root_dentry)
 		return -ENOMEM;
-	}
 	if (MACHINE_IS_VM)
 		rc = hypfs_vm_create_files(sb, root_dentry);
 	else