crypto: mediatek - 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/mediatek/mtk-sha.c

@@ -805,12 +805,9 @@ static int mtk_sha_setkey(struct crypto_ahash *tfm, const u8 *key,
 	size_t ds = crypto_shash_digestsize(bctx->shash);
 	int err, i;
 
-	SHASH_DESC_ON_STACK(shash, bctx->shash);
-
-	shash->tfm = bctx->shash;
-
 	if (keylen > bs) {
-		err = crypto_shash_digest(shash, key, keylen, bctx->ipad);
+		err = crypto_shash_tfm_digest(bctx->shash, key, keylen,
+					      bctx->ipad);
 		if (err)
 			return err;
 		keylen = ds;