[CRYPTO] camellia: Move common code into camellia_setup_tail

Move "key XOR is end of F-function" code part into
camellia_setup_tail(), it is sufficiently similar
between camellia_setup128 and camellia_setup256.
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>