usb: musb: Add support for MediaTek musb controller

usb: musb: Add support for MediaTek musb controller

This adds support for MediaTek musb controller in
host, peripheral and otg mode.
There are some quirk of MediaTek musb controller, such as:
 -W1C interrupt status registers
 -Private data toggle registers
 -No dedicated DMA interrupt line

Signed-off-by: Min Guo <min.guo@mediatek.com>
Signed-off-by: Yonglong Wu <yonglong.wu@mediatek.com>
Signed-off-by: Bin Liu <b-liu@ti.com>
Link: https://lore.kernel.org/r/20200115132547.364-24-b-liu@ti.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>