crypto: ahash - Add padding in crypto_ahash_extsize

The function crypto_ahash_extsize did not include padding when
computing the tfm context size.  This patch fixes this by using
the generic crypto_alg_extsize helper.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/ahash.c

@@ -461,10 +461,10 @@ static int crypto_ahash_init_tfm(struct crypto_tfm *tfm)
 
 static unsigned int crypto_ahash_extsize(struct crypto_alg *alg)
 {
-	if (alg->cra_type == &crypto_ahash_type)
-		return alg->cra_ctxsize;
-
+	if (alg->cra_type != &crypto_ahash_type)
 		return sizeof(struct crypto_shash *);
+
+	return crypto_alg_extsize(alg);
 }
 
 #ifdef CONFIG_NET