pinctrl: sh-pfc: r8a7795: 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 because MOD_SEL register specification for R8A7795
ES2.0 SoC was changed in R-Car Gen3 Hardware User's Manual Rev.0.53E.

Fixes: b205914c ("pinctrl: sh-pfc: r8a7795: Add support for R-Car H3 ES2.0")
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>