crypto: crypto4xx - simplify sa and state context acquisition

Thanks to the big overhaul of crypto4xx_build_pd(), the request-local
sa_in, sa_out and state_record allocation can be simplified.

There's no need to setup any dma coherent memory anymore and
much of the support code can be removed.

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>