xfrm: add rfc4494 AES-CMAC-96 support

Now that CryptoAPI has support for CMAC, we can add support for AES-CMAC-96
(rfc4494).

Cc: Tom St Denis <tstdenis@elliptictech.com>
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>