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

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/ext2/super.c

@@ -1088,9 +1088,8 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 		goto failed_mount3;
 	}
 
-	sb->s_root = d_alloc_root(root);
+	sb->s_root = d_make_root(root);
 	if (!sb->s_root) {
-		iput(root);
 		ext2_msg(sb, KERN_ERR, "error: get root inode failed");
 		ret = -ENOMEM;
 		goto failed_mount3;