BUILD: quic: add some ifdef around the SSL_ERROR_* for libressl

SSL_ERROR_WANT_ASYNC, SSL_ERROR_WANT_ASYNC_JOB and
SSL_ERROR_WANT_CLIENT_HELLO_CB does not seems supported by libressl.
diff --git a/include/haproxy/quic_tls.h b/include/haproxy/quic_tls.h
index 114ed0b..c326ce9 100644
--- a/include/haproxy/quic_tls.h
+++ b/include/haproxy/quic_tls.h
@@ -259,12 +259,14 @@
 		return "WANT_CONNECT";
 	case SSL_ERROR_WANT_ACCEPT:
 		return "WANT_ACCEPT";
+#if !defined(LIBRESSL_VERSION_NUMBER)
 	case SSL_ERROR_WANT_ASYNC:
 		return "WANT_ASYNC";
 	case SSL_ERROR_WANT_ASYNC_JOB:
 		return "WANT_ASYNC_JOB";
 	case SSL_ERROR_WANT_CLIENT_HELLO_CB:
 		return "WANT_CLIENT_HELLO_CB";
+#endif
 	default:
 		return "UNKNOWN";
 	}