usb: image: mdc800: kill download URB on timeout

In the Linux kernel, the following vulnerability has been resolved: usb: image: mdc800: kill download URB on timeout mdc800_device_read() submits download_urb and waits for completion. If the timeout fires and the device has not responded, the function returns without killing the URB, leaving it active. A subsequent read() resubmits the same URB while it is still in-flight, triggering the WARN in usb_submit_urb(): "URB submitted while active" Check the return value of wait_event_timeout() and kill the URB if it indicates timeout, ensuring the URB is complete before its status is inspected or the URB is resubmitted. Similar to - commit 372c93131998 ("USB: yurex: fix control-URB timeout handling") - commit b98d5000c505 ("media: rc: iguanair: handle timeouts")