prevent the primaryGpu is a usb device in multi-gpu scenes

if usb device is the primaryGpu, the device unplug kwin_wayland exit

`   } else if (device->action() == QStringLiteral("remove")) {
            DrmGpu *gpu = findGpu(device->devNum());
            if (gpu) {
                if (primaryGpu() == gpu) {
                    qCCritical(KWIN_DRM) << "Primary gpu has been removed! Quitting...";
                    QCoreApplication::exit(1);
                    return;
                } else {
                    gpu->setRemoved();
                    updateOutputs();
                }
           }`