Allow cgminer to start if usb hotplug is enabled but no devices yet exist.

cgminer.c

@@ -7342,8 +7342,15 @@ int main(int argc, char *argv[])
 			enable_device(devices[i]);
 	}
 
+#ifdef USE_USBUTILS
+	if (!total_devices) {
+		applog(LOG_WARNING, "No devices detected!");
+		applog(LOG_WARNING, "Waiting for USB hotplug devices or press q to quit");
+	}
+#else
 	if (!total_devices)
 		quit(1, "All devices disabled, cannot mine!");
+#endif
 
 	start_devices = total_devices;