clk: renesas: cpg-mssr: Add r8a77470 support

Add RZ/G1C (R8A77470) Clock Pulse Generator / Module Standby and Software
Reset support.

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>