usb: mtu3: register mtu3_irq by threaded irq

Use threaded irq to improve time consuming top-half

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/20220609074233.15532-3-chunfeng.yun@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>