pinctrl: sh-pfc: r8a7795: Add MSIOF pins, groups, and functions

Extracted from a big patch by Takeshi Kihara.
Signed-off-by: NTakeshi Kihara <takeshi.kihara.df@renesas.com>
[geert: Correct MSIOF3 TXD_A/RXD_A pins]
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>