crypto: testmgr - remove unused function argument

The argument "req" of do_one_async_hash_op is not used by the
function. This patch removes this argument and renames the
function to match more closely its purpose.

Signed-off-by: Cristian Stoica <cristian.stoica@freescale.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>