crypto: sahara - Fix dma unmap direction

The direction used in dma_unmap_sg in aes calc is wrong.
This result in the cache not being invalidated correct when aes
calculation is done and result has been dma'ed to memory.
This is seen as sporadic wrong result from aes calc.

Signed-off-by: Mogens Lauridsen <mlauridsen171@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>