crypto: pkcs7: Use match_string() helper to simplify the code

match_string() returns the array index of a matching string.
Use it instead of the open-coded implementation.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Ben Boeckel <mathstuf@gmail.com>

crypto/asymmetric_keys/pkcs7_verify.c

@@ -141,11 +141,10 @@ int pkcs7_get_digest(struct pkcs7_message *pkcs7, const u8 **buf, u32 *len,
 	*buf = sinfo->sig->digest;
 	*len = sinfo->sig->digest_size;
 
-	for (i = 0; i < HASH_ALGO__LAST; i++)
-		if (!strcmp(hash_algo_name[i], sinfo->sig->hash_algo)) {
-			*hash_algo = i;
-			break;
-		}
+	i = match_string(hash_algo_name, HASH_ALGO__LAST,
+			 sinfo->sig->hash_algo);
+	if (i >= 0)
+		*hash_algo = i;
 
 	return 0;
 }