pinctrl: sh-pfc: r8a7796: Add R8A774A1 PFC support

Renesas RZ/G2M (r8a774a1) is pin compatible with R-Car M3-W (r8a7796),
however it doesn't have several automotive specific peripherals. Add
an r8a7796 specific pin groups/functions along with common pin
groups/functions for supporting both r8a7796 and r8a774a1 SoCs.

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>