pinctrl: sh-pfc: Initial R8A7795 PFC support

Add PFC base support for the R8A7795 SoC.

Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
[Morimoto-san: updated]
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>