crypto: mxs-dcp - Fix scatterlist processing

This patch fixes a bug in scatterlist processing that may cause incorrect AES block encryption/decryption.

Fixes: 2e6d793e ("crypto: mxs-dcp - Use sg_mapping_iter to copy data")
Signed-off-by: Tomas Paukrt <tomaspaukrt@email.cz>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>