ipsec_offload: indirect two more functions on the ipsec.ko module load

Specifically, ipsec_accel_on_ifdown() and ipsec_accel_drv_sa_lifetime_update()
should be present in kernel for future mlx5en driver to be statically
linkable into the kernel built with IPSEC_HOOKS + IPSEC_OFFLOAD.

Sponsored by: NVIDIA networking