s3:smbd: Avoid compiler warning for unused label

s3:smbd: Avoid compiler warning for unused label

If either of HAVE_FSTATFS and HAVE_LINUX_MAGIC_H are not defined, gcc
produces the following error:

../../source3/smbd/open.c: In function ‘reopen_from_fsp’:
../../source3/smbd/open.c:1222:1: error: label ‘namebased_open’ defined but not used [-Werror=unused-label]
 1222 | namebased_open:
      | ^~~~~~~~~~~~~~

Signed-off-by: Jo Sutton <josutton@catalyst.net.nz>
Reviewed-by: Martin Schwenke <martin@meltin.net>
Autobuild-User(master): Martin Schwenke <martins@samba.org>
Autobuild-Date(master): Tue Jul  2 04:44:56 UTC 2024 on atb-devel-224