Use a 128-bit swap mask and tbl instruction to simplify the implementation
for generating SM4 rkey_dec.

Also fixed the issue of not being wrapped by kernel_neon_begin/end() when
using the sm4_ce_expand_key() function.
Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>