LU-16796 ofd: Change struct ofd_seq to use refcount_t

LU-16796 ofd: Change struct ofd_seq to use refcount_t

This patch changes struct ofd_seq to use refcount_t
instead of atomic_t

Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: Ie149a6812671ea872e17d2881e52cf6096d147ff
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52722
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>