pinctrl: sh-pfc: r8a7795: Add GP-1-28 port pin support

This patch supports GP-1-28 port pin of R8A7795 ES2.0 SoC added in
Rev.0.54E of the R-Car Gen3 Hardware User's Manual or later version.

Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com>
[geert: Update forgotten PUEN2 entry]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>