pinctrl: uniphier: fix Ethernet (RMII) pin-mux setting for LD20

Fix the pin-mux values for the MDC, MDIO, MDIO_INTL, PHYRSTL pins.

Fixes: fc9da85c ("pinctrl: uniphier: add Ethernet pin-mux settings")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>