tls: rx: assume crypto always calls our callback

If crypto didn't always invoke our callback for async
we'd not be clearing skb->sk and would crash in the
skb core when freeing it. This if must be dead code.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>