pinctrl: sh-pfc: r8a7796: Fix MOD_SEL2 bit26 to 0x0 when using SCK5_A

This patch fixes the implementation incorrect of MOD_SEL2 bit26 value
when SCK5_A pin function is selected for IPSR16 bit[31:28].

This is a correction to the incorrect implementation of MOD_SEL register
pin assignment for R8A7796 SoC specification of R-Car Gen3 Hardware
User's Manual Rev.0.51E or later.

Fixes: f9aece73

 ("pinctrl: sh-pfc: Initial R8A7796 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>