usb: xhci-mtk: disable all ports when disable host controller

This is used to avoid the ports status of IPPC being brought in kernel
stage, it may cause ports error especially when the xhci controller is
a component of dual-role controller.

Reported-by: Yun-Chien Yu <yun-chien.yu@mediatek.com>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>