Adapt call of ssh_add_identity_constrained() after openssh update

Note, this commit log entry belongs to the previous commit (1.31)
and is to fix my screwup in the previous commit,   Apologies all.

With the recent openssh update, ssh_add_identity_constrained() has had
its "maxsign" parameter removed.  Adapt the mapping macro from
ssh_add_identity() -> ssh_add_identity_constrained() to cope.

While here, change the octal 0 (00) that was being passed to as the
final (size_t) arg to be a nice simple decimal 0 instead.

This should fix the current build breakage.

Author: kre

lib/libpam/modules/pam_ssh/pam_ssh.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: pam_ssh.c,v 1.31 2025/10/12 08:50:30 kre Exp $	*/
+/*	$NetBSD: pam_ssh.c,v 1.32 2025/10/12 08:58:13 kre Exp $	*/
 
 /*-
  * Copyright (c) 2003 Networks Associates Technology, Inc.
@@ -38,7 +38,7 @@
 #ifdef __FreeBSD__
 __FBSDID("$FreeBSD: src/lib/libpam/modules/pam_ssh/pam_ssh.c,v 1.40 2004/02/10 10:13:21 des Exp $");
 #else
-__RCSID("$NetBSD: pam_ssh.c,v 1.31 2025/10/12 08:50:30 kre Exp $");
+__RCSID("$NetBSD: pam_ssh.c,v 1.32 2025/10/12 08:58:13 kre Exp $");
 #endif
 
 #include <sys/param.h>