crypto: mcryptd - pass through absence of ->setkey()

When the mcryptd template is used to wrap an unkeyed hash algorithm,
don't install a ->setkey() method to the mcryptd instance.  This change
is necessary for mcryptd to keep working with unkeyed hash algorithms
once we start enforcing that ->setkey() is called when present.

Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>