pinctrl: sh-pfc: r8a7795: Fix MOD_SEL1 bit[25:24] to 0x3 when using STP_ISEN_1_D

This patch fixes the implementation incorrect of MOD_SEL1 bit[25:24]
value when STP_ISEN_1_D pin function is selected for IPSR17 bit[27:24].

This is a correction to the incorrect implementation of MOD_SEL register
pin assignment for R8A7795 SoC specification of R-Car Gen3 Hardware
User's Manual Rev.0.51E or later.

Fixes: 0b0ffc96 ("pinctrl: sh-pfc: Initial R8A7795 PFC support")
Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>