usb: mtu3: fix U3 port link issue

the issue is introduced when @is_u3_ip is used in mtu3_device_enabe()
before initialized in mtu3_mem_alloc(), so get global IP information
at first before used by following functins.

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