soc: renesas: rcar-sysc: Add r8a77470 support

Add support for RZ/G1C (R8A77470) SoC power areas to the R-Car SYSC
driver.

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