there is a reference clock for each port, HighSpeed port is 48M,
and SuperSpeed port is usually 26M. it is flexible to move it
into port node, then unused clock can be disabled.
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>