crypto: chelsio - Fix an error code in chcr_hash_dma_map()

The dma_map_sg() function returns zero on error and positive values on
success.  We want to return -ENOMEM on failure here and zero on success.

Fixes: 2f47d580 ("crypto: chelsio - Move DMA un/mapping to chcr from lld cxgb4 driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>