crypto: sun8i-ss - do not zeroize all pad

Instead of memset all pad buffer, it is faster to only put 0 where
needed.
Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/allwinner/sun8i-ss/sun8i-ss-hash.c

@@ -319,7 +319,7 @@ int sun8i_ss_hash_run(struct crypto_engine *engine, void *breq)
 	unsigned int len;
 	u64 fill, min_fill, byte_count;
 	void *pad, *result;
-	int j, i, todo;
+	int j, i, k, todo;
 	__be64 *bebits;
 	__le64 *lebits;
 	dma_addr_t addr_res, addr_pad;
@@ -334,7 +334,6 @@ int sun8i_ss_hash_run(struct crypto_engine *engine, void *breq)
 
 	result = ss->flows[rctx->flow].result;
 	pad = ss->flows[rctx->flow].pad;
-	memset(pad, 0, algt->alg.hash.halg.base.cra_blocksize * 2);
 	bf = (__le32 *)pad;
 
 	for (i = 0; i < MAX_SG; i++) {
@@ -395,7 +394,10 @@ int sun8i_ss_hash_run(struct crypto_engine *engine, void *breq)
 	if (fill < min_fill)
 		fill += 64;
 
+	k = j;
 	j += (fill - min_fill) / sizeof(u32);
+	for (; k < j; k++)
+		bf[k] = 0;
 
 	switch (algt->ss_algo_id) {
 	case SS_ID_HASH_MD5: