crypto: lrw - add interface for parallelized cipher implementions

Export gf128mul table initialization routines and add lrw_crypt() function
that can be used by cipher implementations that can benefit from parallelized
cipher operations.

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