crypto: poly1305 - remove cra_alignmask

Now that nothing in poly1305-generic assumes any special alignment,
remove the cra_alignmask so that the crypto API does not have to
unnecessarily align the buffers.

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