usb: mtu3: fix error of xhci port id when enable U3 dual role

If dual role mode is enabled, when switch u3port0 to device mode,
it will affect port id calculation of host(xHCI), specially when
host supports multi U2 ports or U3 ports, so need enable its dual
role mode, and fix it here.

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