pinctrl: sh-pfc: r8a7796: Fix IPSR setting for MSIOF3_SS1_E pin

This patch fixes the IPSR register setting when the MSIOF3_SS1_E pin
function is selected.

This is a correction to the incorrect implementation of IPSR 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>
[geert: Reword]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>