usb: host: xhci-mtk: omit shared hcd if either root hub has no ports

There is error log when add a usb3 root hub without ports:
"hub 4-0:1.0: config failed, hub doesn't have any ports! (err -19)"

so omit the shared hcd if either of the root hubs has no ports, but
usually there is no usb3 port.

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20221118110116.20165-1-chunfeng.yun@mediatek.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>