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/sysv/super.c b/fs/sysv/super.c
index f467740..7491c33 100644
--- a/fs/sysv/super.c
+++ b/fs/sysv/super.c
@@ -341,9 +341,8 @@
 		printk("SysV FS: get root inode failed\n");
 		return 0;
 	}
-	sb->s_root = d_alloc_root(root_inode);
+	sb->s_root = d_make_root(root_inode);
 	if (!sb->s_root) {
-		iput(root_inode);
 		printk("SysV FS: get root dentry failed\n");
 		return 0;
 	}