crypto: sa2ul - Use proper helpers to setup request

Rather than setting up a request by hand, use the correct API helpers
to setup the new request.  This is because the API helpers will setup
chaining.

Also change the fallback allocation to explicitly request for a
sync algorithm as this driver will crash if given an async one.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Manorit Chawdhry <m-chawdhry@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>