crypto: twofish-x86-asm - make assembler functions use twofish_ctx instead of crypto_tfm

This needed by 3-way twofish patch to be able to easily use one block
assembler functions. As glue code is shared between i586/x86_64 apply
change to i586 assembler too. Also export assembler functions for
3-way parallel twofish module.

CC: Joachim Fritschi <jfritschi@freenet.de>
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>