usbutils - avoid free cgusb twice

usbutils.c

@@ -845,12 +845,16 @@ static struct cg_usb_device *free_cgusb(struct cg_usb_device *cgusb)
 
 void usb_uninit(struct cgpu_info *cgpu)
 {
+	// May have happened already during a failed initialisation
+	//  if release_cgpu() was called due to a USB NODEV(err)
+	if (!cgpu->usbdev)
+		return;
 	libusb_release_interface(cgpu->usbdev->handle, cgpu->usbdev->found->interface);
 	libusb_close(cgpu->usbdev->handle);
 	cgpu->usbdev = free_cgusb(cgpu->usbdev);
 }
 
-void release_cgpu(struct cgpu_info *cgpu)
+static void release_cgpu(struct cgpu_info *cgpu)
 {
 	struct cg_usb_device *cgusb = cgpu->usbdev;
 	struct cgpu_info *lookcgpu;

usbutils.h

@@ -129,7 +129,6 @@ struct device_drv;
 struct cgpu_info;
 
 void usb_uninit(struct cgpu_info *cgpu);
-void release_cgpu(struct cgpu_info *cgpu);
 bool usb_init(struct cgpu_info *cgpu, struct libusb_device *dev, struct usb_find_devices *found);
 void usb_detect(struct device_drv *drv, bool (*device_detect)(struct libusb_device *, struct usb_find_devices *));
 struct api_data *api_usb_stats(int *count);