fs: Fix error checking for d_hash_and_lookup()

The d_hash_and_lookup() function returns error pointers or NULL.
Most incorrect error checks were fixed, but the one in int path_pts()
was forgotten.

Fixes: eedf265a ("devpts: Make each mount of devpts an independent filesystem.")
Signed-off-by: Wang Ming <machel@vivo.com>
Message-Id: <20230713120555.7025-1-machel@vivo.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/namei.c

@@ -2890,7 +2890,7 @@ int path_pts(struct path *path)
 	dput(path->dentry);
 	path->dentry = parent;
 	child = d_hash_and_lookup(parent, &this);
-	if (!child)
+	if (IS_ERR_OR_NULL(child))
 		return -ENOENT;
 
 	path->dentry = child;