exfat: fix passing zero to ERR_PTR() in exfat_mkdir()

Detected by Smatch.

namei.c:890 exfat_mkdir() warn:
	passing zero to 'ERR_PTR'

Signed-off-by: Yang Wen <anmuxixixi@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

Author: anmuxixixi

fs/exfat/namei.c

@@ -874,9 +874,10 @@ static struct dentry *exfat_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 
 	i_pos = exfat_make_i_pos(&info);
 	inode = exfat_build_inode(sb, &info, i_pos);
-	err = PTR_ERR_OR_ZERO(inode);
-	if (err)
+	if (IS_ERR(inode)) {
+		err = PTR_ERR(inode);
 		goto unlock;
+	}
 
 	inode_inc_iversion(inode);
 	EXFAT_I(inode)->i_crtime = simple_inode_init_ts(inode);
@@ -887,7 +888,7 @@ static struct dentry *exfat_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 
 unlock:
 	mutex_unlock(&EXFAT_SB(sb)->s_lock);
-	return ERR_PTR(err);
+	return err ? ERR_PTR(err) : NULL;
 }
 
 static int exfat_check_dir_empty(struct super_block *sb,