[CRYPTO] digest: Remove unnecessary zeroing during init

Various digest algorithms operate one block at a time and therefore
keep a temporary buffer of partial blocks.  This buffer does not need
to be initialised since there is a counter which indicates what is and
isn't valid in it.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/sha256.c

@@ -242,7 +242,6 @@ static void sha256_init(void *ctx)
 	sctx->state[6] = H6;
 	sctx->state[7] = H7;
 	sctx->count[0] = sctx->count[1] = 0;
-	memset(sctx->buf, 0, sizeof(sctx->buf));
 }
 
 static void sha256_update(void *ctx, const u8 *data, unsigned int len)