crypto: n2 - use crypto_shash_tfm_digest()

Instead of manually allocating a 'struct shash_desc' on the stack and
calling crypto_shash_digest(), switch to using the new helper function
crypto_shash_tfm_digest() which does this for us.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/n2_core.c

@@ -462,7 +462,6 @@ static int n2_hmac_async_setkey(struct crypto_ahash *tfm, const u8 *key,
 	struct n2_hmac_ctx *ctx = crypto_ahash_ctx(tfm);
 	struct crypto_shash *child_shash = ctx->child_shash;
 	struct crypto_ahash *fallback_tfm;
-	SHASH_DESC_ON_STACK(shash, child_shash);
 	int err, bs, ds;
 
 	fallback_tfm = ctx->base.fallback_tfm;
@@ -470,13 +469,11 @@ static int n2_hmac_async_setkey(struct crypto_ahash *tfm, const u8 *key,
 	if (err)
 		return err;
 
-	shash->tfm = child_shash;
-
 	bs = crypto_shash_blocksize(child_shash);
 	ds = crypto_shash_digestsize(child_shash);
 	BUG_ON(ds > N2_HASH_KEY_MAX);
 	if (keylen > bs) {
-		err = crypto_shash_digest(shash, key, keylen,
+		err = crypto_shash_tfm_digest(child_shash, key, keylen,
 					      ctx->hash_key);
 		if (err)
 			return err;