gcm_ghash_4bit
void gcm_ghash_4bit(u64 Xi[2],const u128 Htable[16],const u8 *inp,size_t len);
#define GHASH(ctx,in,len) gcm_ghash_4bit((ctx)->Xi.u,(ctx)->Htable,in,len)
ctx->ghash = gcm_ghash_4bit;
ctx->ghash = gcm_ghash_4bit;