pinctrl: uniphier: split pinctrl driver for PH1-LD11 and PH1-LD20

PH1-LD11 and PH1-LD20 have much pin controlling in common, so I
added a single driver shared between them in the initial commit.

However, the Ethernet pin-mux settings I am going to add are
different with each other, and they may diverge more as the
progress of development.  Split it into two dedicated drivers.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>