crypto: inside-secure - do not use areq->result for partial results

This patches update the SafeXcel driver to stop using the crypto
ahash_request result field for partial results (i.e. on updates).
Instead the driver local safexcel_ahash_req state field is used, and
only on final operations the ahash_request result buffer is updated.

Fixes: 1b44c5a6

 ("crypto: inside-secure - add SafeXcel EIP197 crypto engine driver")
Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>