tls: drop unnecessary cipher_type checks in tls offload

We should never reach tls_device_reencrypt, tls_enc_record, or
tls_enc_skb with a cipher_type that can't be offloaded. Replace those
checks with a DEBUG_NET_WARN_ON_ONCE, and use cipher_desc instead of
hard-coding offloadable cipher types.

Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>