crypto: twofish-x86_64/i586 - set alignmask to zero

x86 has fast unaligned accesses, so twofish-x86_64/i586 does not need to enforce
alignment.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>