crypto: chcr - checking for IS_ERR() instead of NULL

The create_hash_wr() function never returns error pointers.  It returns
NULL on error.

Fixes: 358961d1

 ("crypto: chcr - Added new structure chcr_wr")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>