crypto: serpent-sse2 - prepare serpent-sse2 glue code into generic x86 glue code for 128bit block ciphers

Block cipher implementations in arch/x86/crypto/ contain common glue code that
is currently duplicated in each module (camellia-x86_64, twofish-x86_64-3way,
twofish-avx, serpent-sse2 and serpent-avx). This patch prepares serpent-sse2
glue into generic glue code for all 128bit block ciphers to use in
arch/x86/crypto.
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>