usb: Add MediaTek USB3 DRD driver

This patch adds support for the MediaTek USB3 controller
integrated into MT8173. It currently supports High-Speed
Peripheral Only mode.

Super-Speed Peripheral, Dual-Role Device and Host Only (xHCI)
modes will be added in the next patchs.

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>