cxgb4/ch_ipsec: Registering xfrmdev_ops with cxgb4

As ch_ipsec was removed without clearing xfrmdev_ops and netdev
feature(esp-hw-offload). When a recalculation of netdev feature is
triggered by changing tls feature(tls-hw-tx-offload) from user
request, it causes a page fault due to absence of valid xfrmdev_ops.

Fixes: 6dad4e8a ("chcr: Add support for Inline IPSec")
Signed-off-by: Ayush Sawal <ayush.sawal@chelsio.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>