Allow cmac to be cloned.  The underlying cipher needs to support
cloning by not having a cra_init function (all implementations of
aes that do not require a fallback can be cloned).
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>