crypto: serpent - rename module from serpent to serpent_generic

Rename module from serpent.ko to serpent_generic.ko and add module alias. This
is to allow assembler implementation to autoload on 'modprobe serpent'. Also
add driver_name and priority for serpent cipher.

CC: Dag Arne Osvik <osvik@ii.uib.no>
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>