Bluetooth: btusb: Return error code when getting patch status failed

If there are failure cases in getting patch status, it should return the
error code (-EIO).

Fixes: fc342c4d ("Bluetooth: btusb: Add protocol support for MediaTek MT7921U USB devices")
Co-developed-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Mark Chen <mark-yw.chen@mediatek.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>