* cipher/sm4.c (sm4_expand_key): Prefetch sbox table.
(sm4_get_crypt_blk1_16_fn): Do not prefetch sbox table.
(sm4_expand_key, _gcry_sm4_ctr_enc, _gcry_sm4_cbc_dec)
(_gcry_sm4_cfb_dec): Prefetch sbox table if table look-up
implementation is used.