arm: dts: mt7623: remove useless property pinctrl-names at node switch@0

arm: dts: mt7623: remove useless property pinctrl-names at node switch@0

The property pinctrl-names is totally superfluous. It would be good to
remove the property to keep the node neatness. There is actually
unnecessary to set up any pins for data path TRGMII between main SoC and
MT7530. Furthermore, it's more reasonable for the pin setup of control
path MDIO bus is being placed inside the node of ethernet controller.

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>