crypto: serpent-sse2 - combine ablk_*_init functions

Driver name in ablk_*_init functions can be constructed runtime. Therefore
use single function ablk_init to reduce object size.

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