Cast ca_list to (void *) to silence msvc warning 4090

Change-Id: If1fad46f14286ba98b86754605731a7be31de901
Reviewed-on: https://boringssl-review.googlesource.com/2680
Reviewed-by: Adam Langley <agl@google.com>

ssl/ssl_ciph.c

@@ -1070,7 +1070,7 @@ ssl_create_cipher_list(const SSL_PROTOCOL_METHOD *ssl_method,
     ok = ssl_cipher_process_rulestr(rule_p, &head, &tail, ca_list);
   }
 
-  OPENSSL_free(ca_list); /* Not needed anymore */
+  OPENSSL_free((void *)ca_list); /* Not needed anymore */
 
   if (!ok) {
     goto err;