crypto: essiv - 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 <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

crypto/essiv.c

···
 				 const u8 *key, unsigned int keylen)
 {
 	struct essiv_tfm_ctx *tctx = crypto_skcipher_ctx(tfm);
-	SHASH_DESC_ON_STACK(desc, tctx->hash);
 	u8 salt[HASH_MAX_DIGESTSIZE];
 	int err;
 
···
 	if (err)
 		return err;
 
-	desc->tfm = tctx->hash;
-	err = crypto_shash_digest(desc, key, keylen, salt);
+	err = crypto_shash_tfm_digest(tctx->hash, key, keylen, salt);
 	if (err)
 		return err;