pinctrl: renesas: r8a779g0: Tidyup POC1 voltage

According to Rev.0.51 datasheet 004_R-CarV4H_pin_function.xlsx,
GP1_23 - GP1_28 are 1.8/3.3V.  But they are not on Table 7.28.
According to the HW team, there are no bits assigned.
This patch follows HW team's comment.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/8735fltxwg.wl-kuninori.morimoto.gx@renesas.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>