FreeBSD: stop passing LK_INTERLOCK to VOP_LOCK

There is an ongoing effort to eliminate this feature.

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Closes #13908