We can simplify the blowfish-x86_64 glue code by using the preexisting
ECB/CBC helper macros. Additionally, this allows for easier reuse of asm
functions in later x86 implementations of blowfish.

This involves:
 1 - Modifying blowfish_dec_blk_4way() to xor outputs when a flag is
     passed.
 2 - Renaming blowfish_dec_blk_4way() to __blowfish_dec_blk_4way().
 3 - Creating two wrapper functions around __blowfish_dec_blk_4way() for
     use in the ECB/CBC macros.
 4 - Removing the custom ecb_encrypt() and cbc_encrypt() routines in
     favor of macro-based routines.
Signed-off-by: Peter Lafreniere <peter@n8pjl.ca>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>