crypto: x86/sm4 - export reusable AESNI/AVX functions

Export the reusable functions in the SM4 AESNI/AVX implementation,
mainly public functions, which are used to develop the SM4 AESNI/AVX2
implementation, and eliminate unnecessary duplication of code.

At the same time, in order to make the public function universal,
minor fixes was added.

Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>