crypto: x86/chacha20 - Remove cra_alignmask

Now that the generic ChaCha20 implementation no longer needs a
cra_alignmask, the x86 one doesn't either -- given that the x86
implementation doesn't need the alignment itself.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>