pinctrl: uniphier: add Ethernet pin-mux settings

Add the following Ethernet interfaces:

  PH1-LD4: MII, RMII
  PH1-Pro4: MII, RMII, RGMII
  PH1-sLD8: MII, RMII (Built-in PHY is also supported)
  ProXstream2: MII, RMII, RGMII
  PH1-LD6b: RMII, RGMII
  PH1-LD11: RMII (Built-in PHY is also supported)
  PH1-LD20: RMII, RGMII

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>