usb: xhci-mtk: fix list_del warning when enable list debug

There is warning of 'list_del corruption' when enable list debug
(CONFIG_DEBUG_LIST=y), fix it by using list_del_init()

Fixes: 4ce18666 ("usb: xhci-mtk: Do not use xhci's virt_dev in drop_endpoint")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/20211209025422.17108-1-chunfeng.yun@mediatek.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>