pinctrl: sh-pfc: r8a7796: Fix MOD_SEL register pin assignment for SSI pins group

pinctrl: sh-pfc: r8a7796: Fix MOD_SEL register pin assignment for SSI pins group

This patch fixes MOD_SEL1 bit20 and MOD_SEL2 bit20, bit21 pin assignment
for SSI pins group.

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: f9aece7344bd ("pinctrl: sh-pfc: Initial R8A7796 PFC support")
Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
Signed-off-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>