crypto: aesni - remove unused defines in "by8" variant

The defines for xkey3, xkey6 and xkey9 are not used in the code. They're
probably left overs from merging the three source files for 128, 192 and
256 bit AES. They can safely be removed.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Chandramouli Narayanan <mouli@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>