crypto: talitos - fix hash result for VMAP_STACK

When VMAP_STACK is selected, stack cannot be DMA-mapped.
Therefore, the hash result has to be DMA-mapped in the request
context and copied into areq->result at completion.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>