unifies encrypt/decrypt routines for different key lengths.
This reduces module size by ~25%, with tiny (less than 1%)
speed impact.
Also collapses encrypt/decrypt into more readable
(visually shorter) form using macros.
Signed-off-by: NDenys Vlasenko <vda.linux@googlemail.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>