This integrates both the accelerated scalar and the NEON implementations
of SHA-224/256 as well as SHA-384/512 from the OpenSSL project.

Relative performance compared to the respective generic C versions:

                 |  SHA256-scalar  | SHA256-NEON* |  SHA512  |
     ------------+-----------------+--------------+----------+
     Cortex-A53  |      1.63x      |     1.63x    |   2.34x  |
     Cortex-A57  |      1.43x      |     1.59x    |   1.95x  |
     Cortex-A73  |      1.26x      |     1.56x    |     ?    |

The core crypto code was authored by Andy Polyakov of the OpenSSL
project, in collaboration with whom the upstream code was adapted so
that this module can be built from the same version of sha512-armv8.pl.

The version in this patch was taken from OpenSSL commit 32bbb62ea634
("sha/asm/sha512-armv8.pl: fix big-endian support in __KERNEL__ case.")

* The core SHA algorithm is fundamentally sequential, but there is a
  secondary transformation involved, called the schedule update, which
  can be performed independently. The NEON version of SHA-224/SHA-256
  only implements this part of the algorithm using NEON instructions,
  the sequential part is always done using scalar instructions.
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>