This adds ARMv8 NEON implementations of SM4 in ECB, CBC, CFB and CTR
modes. This implementation uses the plain NEON instruction set, All
S-BOX substitutions uses the tbl/tbx instructions of ARMv8, combined
with the out-of-order execution in CPU, this optimization supports
encryption of up to 8 blocks at the same time.

The performance of encrypting one block is not as good as software
implementation, so the encryption operations of CBC and CFB still
use pure software algorithms.

Benchmark on T-Head Yitian-710 2.75 GHz, the data comes from the 218
mode of tcrypt. The abscissas are blocks of different lengths. The
data is tabulated and the unit is Mb/s:

sm4-generic |     16       64      128      256     1024     1420     4096
    ECB enc |  80.05    91.42    93.66    94.77    95.69    95.77    95.86
    ECB dec |  79.98    91.41    93.64    94.76    95.66    95.77    95.85
    CBC enc |  78.55    86.50    88.02    88.77    89.36    89.42    89.48
    CBC dec |  76.82    89.06    91.52    92.77    93.75    93.83    93.96
    CFB enc |  77.64    86.13    87.62    88.42    89.08    88.83    89.18
    CFB dec |  77.57    88.34    90.36    91.45    92.34    92.00    92.44
    CTR enc |  77.80    88.28    90.23    91.22    92.11    91.81    92.25
    CTR dec |  77.83    88.22    90.22    91.22    92.04    91.82    92.28
sm4-neon
    ECB enc |  28.31   112.77   203.03   209.89   215.49   202.11   210.59
    ECB dec |  28.36   113.45   203.23   210.00   215.52   202.13   210.65
    CBC enc |  79.32    87.02    88.51    89.28    89.85    89.89    89.97
    CBC dec |  28.29   112.20   203.30   209.82   214.99   201.51   209.95
    CFB enc |  79.59    87.16    88.54    89.30    89.83    89.62    89.92
    CFB dec |  28.12   111.05   202.47   209.02   214.21   210.90   209.12
    CTR enc |  28.04   108.81   200.62   206.65   211.78   208.78   206.74
    CTR dec |  28.02   108.82   200.45   206.62   211.78   208.74   206.70
Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>