UDP: Protect call to UDP API based on feature

Fails to compile in some qtlite setup

Pick-to: 6.7 6.6 6.5
Change-Id: If04c1ca3f1b4eb59517902b8caab167f4627391b
Reviewed-by: Jari Helaakoski <jari.helaakoski@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/network/socket/qabstractsocket.cpp

@@ -643,7 +643,11 @@ bool QAbstractSocketPrivate::canReadNotification()
             socketEngine->setReadNotificationEnabled(false);
             return true;
         }
-        if (!isUdpSocket || socketEngine->hasPendingDatagrams()) {
+        if (!isUdpSocket
+#if QT_CONFIG(udpsocket)
+            || socketEngine->hasPendingDatagrams()
+#endif
+        ) {
             hasPendingData = true;
             hasPendingDatagram = isUdpSocket;
         }