crypto: ctr - make rfc3686 asynchronous block cipher

Some hardware crypto drivers register asynchronous ctr(aes), which is left
unused in IPSEC because rfc3686 template only supports synchronous block
ciphers. Some other drivers register rfc3686(ctr(aes)) to workaround this
limitation but not all.

This patch changes rfc3686 to use asynchronous block ciphers, to allow async
ctr(aes) algorithms to be utilized automatically by IPSEC.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>