smbd: fix mode being sent to possibly_set_archive

smbd: fix mode being sent to possibly_set_archive

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15880

possibly_set_archive is being passed smb_fname->st.st_ex_mode.
Inside the function same variable is getting assigned to itself.
Fixed this to send unx_mode to possibly_set_archive.

Signed-off-by: Srinivas Rao V <Srinivas.Rao.V@ibm.com>
Reviewed-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Guenther Deschner <gd@samba.org>
Autobuild-User(master): Günther Deschner <gd@samba.org>
Autobuild-Date(master): Fri Jul 18 22:25:05 UTC 2025 on atb-devel-224

(cherry picked from commit 1d1acebf01902bef3a9ccae23c3be4cacbb777b2)

Autobuild-User(v4-21-test): Jule Anger <janger@samba.org>
Autobuild-Date(v4-21-test): Thu Aug 14 09:41:57 UTC 2025 on atb-devel-224