media: gspca: Fix memory leak in probe

The gspca driver leaks memory when a probe fails.  gspca_dev_probe2()
calls v4l2_device_register(), which takes a reference to the
underlying device node (in this case, a USB interface).  But the
failure pathway neglects to call v4l2_device_unregister(), the routine
responsible for dropping this reference.  Consequently the memory for
the USB interface and its device never gets released.

This patch adds the missing function call.

Reported-and-tested-by: syzbot+44e64397bd81d5e84cba@syzkaller.appspotmail.com
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: <stable@vger.kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/usb/gspca/gspca.c

@@ -1575,6 +1575,7 @@ int gspca_dev_probe2(struct usb_interface *intf,
 		input_unregister_device(gspca_dev->input_dev);
 #endif
 	v4l2_ctrl_handler_free(gspca_dev->vdev.ctrl_handler);
+	v4l2_device_unregister(&gspca_dev->v4l2_dev);
 	kfree(gspca_dev->usb_buf);
 	kfree(gspca_dev);
 	return ret;