[CRYPTO] api: Allow ablkcipher with no queues

Evgeniy's hifn driver and probably mine don't use ablkcipher->queue at all. 
The show method of ablkcipher will access this field without checking if it 
is valid.

Signed-off-by: Sebastian Siewior <linux-crypto@ml.breakpoint.cc>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>